How to Quit Smoking: The Complete Guide to Stopping for Good

Tobacco kills more than eight million people every year, according to the World Health Organization, including more than a million non-smokers exposed to second-hand smoke. Up to half of all long-term smokers will die from a smoking-related disease, losing on average around ten years of life. Yet stopping smoking at any age brings rapid and substantial health benefits, and people who stop before the age of 40 avoid most of the excess risk of dying from smoking.

Most smokers want to stop, and many try every year. The problem is not a lack of willpower: nicotine is one of the most addictive substances known, and quitting without support has the lowest success rate of all methods. Combining behavioural support with stop-smoking medicines can roughly double or triple your chances of success. This complete guide explains how nicotine addiction works, what happens to your body when you stop, the methods with the best evidence, how to handle withdrawal and cravings, the role of vapes, how to avoid weight gain, how to recover from a slip, and how to quit in pregnancy and other special situations.

Why is quitting so hard?

Nicotine addiction

When you inhale cigarette smoke, nicotine reaches your brain within about ten seconds. It triggers the release of dopamine, a chemical linked to pleasure and reward. Over time, the brain adapts by producing more nicotine receptors. When nicotine levels fall, these receptors create cravings and withdrawal symptoms such as irritability, anxiety, low mood, poor concentration and restlessness. Smoking a cigarette relieves these symptoms, which reinforces the cycle. Many smokers believe cigarettes relieve stress, but much of that “stress relief” is actually relief of nicotine withdrawal that began after the last cigarette.

Habit and triggers

Smoking also becomes linked to daily routines and emotions: the first cigarette with morning coffee, after meals, on breaks at work, when driving, with alcohol, when stressed or bored, or with certain friends. These cues trigger cravings automatically, even after physical withdrawal has passed.

Social and environmental factors

Having family members, friends or colleagues who smoke, living in environments where cigarettes are cheap and easy to buy, and marketing by the tobacco industry all make quitting harder.

Understanding these three parts, the chemical addiction, the habits and the environment, helps explain why the most effective approaches tackle all three.

What happens when you stop smoking?

The benefits begin within minutes and continue for years:

• Within 20 minutes: heart rate and blood pressure begin to fall.
• Within 12 to 24 hours: carbon monoxide levels in the blood fall to normal, and oxygen levels improve.
• Within 2 to 12 weeks: circulation improves and lung function begins to increase. Walking and exercise become easier.
• Within 1 to 9 months: coughing and shortness of breath decrease. The tiny hair-like structures in the lungs (cilia) recover and clear mucus more effectively, reducing infections.
• Within 1 year: the excess risk of coronary heart disease is about half that of someone who continues to smoke.
• Within 5 to 15 years: the risk of stroke falls towards that of a non-smoker. The risk of cancers of the mouth, throat, oesophagus and bladder is halved within about 5 to 10 years.
• Within 10 years: the risk of dying from lung cancer is about half that of someone who still smokes.
• Within 15 years: the risk of coronary heart disease is close to that of a non-smoker.

Other benefits include better sense of taste and smell, healthier skin and teeth, improved fertility, lower risk of erectile dysfunction, better wound healing and surgery outcomes, money saved, and protecting family members from second-hand smoke. Stopping smoking also improves mental health: studies show reductions in anxiety, depression and stress after quitting.

The methods that work best

Research involving hundreds of thousands of people has identified clearly which approaches are most effective:

1. Combining behavioural support with stop-smoking medicine is the most effective approach. Specialist stop-smoking services, where available, offer this combination and can triple your chance of quitting compared with going it alone.
2. Stop-smoking medicines on their own, including nicotine replacement therapy (NRT), varenicline and cytisine, roughly double quit rates.
3. Behavioural support on its own, through counselling, group sessions, telephone quitlines, text message programmes or apps, also increases success.
4. Quitting with willpower alone (“cold turkey” without support) works for some people, but has the lowest success rate, with only a small percentage still not smoking a year later.

The message is simple: get help, and use medicine. It is not cheating; it is using the most effective tools available.

Nicotine replacement therapy (NRT)

NRT provides nicotine without the tar, carbon monoxide and thousands of other toxic chemicals in tobacco smoke. It reduces withdrawal symptoms and cravings, allowing you to focus on breaking the habit. It is the smoke, not the nicotine, that causes most of the harm from smoking.

Types of NRT

• Patches: provide a steady level of nicotine over 16 or 24 hours. Easy to use and discreet.
• Gum: chewed slowly until the taste becomes strong, then “parked” between the cheek and gum, then chewed again.
• Lozenges: dissolve slowly in the mouth.
• Mouth spray: fast-acting, good for sudden cravings.
• Nasal spray: the fastest-acting form, useful for heavy smokers.
• Inhalator: a plastic device that looks like a cigarette, which helps with the hand-to-mouth habit.
• Microtabs: small tablets dissolved under the tongue.

Combination NRT works best

Using a patch plus a fast-acting form (gum, lozenge, spray or inhalator) is significantly more effective than a single type. The patch provides a steady background level of nicotine, and the fast-acting product handles breakthrough cravings.

Using NRT properly

• Use enough. Many people under-dose. Heavy smokers often need a higher-strength patch plus regular fast-acting doses.
• Use it for long enough, usually at least 8 to 12 weeks, then reduce gradually.
• Use fast-acting products regularly, not just when a craving is unbearable.
• It is safe to start NRT before your quit date and cut down gradually (“cut down to quit”), if that suits you better.
• If you slip and smoke while using NRT, keep using the NRT and get back on track.

Common side effects include skin irritation from patches (move the patch site daily), vivid dreams (remove 24-hour patches at night), hiccups and mouth irritation from oral products. NRT is safe for most people, including those with stable heart disease. It is far safer than continuing to smoke.

Varenicline

Varenicline is a prescription tablet that acts on nicotine receptors in the brain. It reduces cravings and withdrawal, and also reduces the satisfaction of smoking if you do smoke. It is one of the most effective single stop-smoking medicines.

• You start taking it one to two weeks before your quit date, gradually increasing the dose, and usually continue for 12 weeks.
• The most common side effect is nausea, which can be reduced by taking it with food and a full glass of water. Other side effects include vivid dreams, sleep disturbance and headache.
• Earlier concerns about serious psychiatric side effects were not confirmed in a large international safety study, but anyone with changes in mood or behaviour should stop and seek advice.
• Availability varies between countries.

Cytisine (cytisinicline)

Cytisine is a plant-derived medicine that works in a similar way to varenicline. It has been used in Central and Eastern Europe for decades and is now available or under evaluation in more countries. It is typically taken for 25 days, is inexpensive, and studies show it is at least as effective as NRT and comparable to varenicline in some trials. It is included on the WHO Model List of Essential Medicines, which may increase access in many countries.

Bupropion

Bupropion is an antidepressant that also helps people stop smoking. It is started one to two weeks before the quit date and taken for 7 to 9 weeks. It is not suitable for people with a history of seizures, eating disorders or certain other conditions. It is less widely used than NRT and varenicline.

Vapes (e-cigarettes)

E-cigarettes heat a liquid, usually containing nicotine, into an aerosol that is inhaled. They do not burn tobacco, so they expose users to far fewer toxic chemicals than cigarettes. Evidence from systematic reviews shows that nicotine e-cigarettes can help smokers stop smoking, and in some trials they were more effective than NRT.

Positions on vaping differ between countries and organisations:

• Some health authorities, for example in the United Kingdom and New Zealand, support vaping as a quitting aid for adult smokers, while emphasising that people who do not smoke should not vape.
• The World Health Organization and many other countries are more cautious, highlighting uncertainty about long-term effects, the risk of young people taking up vaping, and tobacco industry involvement. Some countries ban or strictly restrict vapes.

Key points if you are considering vaping to quit:

• Vaping is not risk-free, but for adult smokers it is substantially less harmful than continuing to smoke.
• The aim should be to switch completely. Using vapes and smoking at the same time (“dual use”) gives much less health benefit.
• Use regulated products from reputable sources, follow local laws, and never add other substances.
• Once you have stopped smoking, plan to reduce and eventually stop vaping too.
• Young people and non-smokers should not start vaping.

Behavioural support

Medicines help with the chemical addiction; behavioural support helps with the habits, triggers and emotions. Options include:

• Specialist stop-smoking services: one-to-one or group sessions with trained advisers, often free. They typically offer weekly support for the first few weeks.
• Telephone quitlines: available in many countries, offering counselling by phone.
• Text message programmes and apps: provide daily tips, encouragement and craving support. Several have evidence of benefit.
• Brief advice from nurses, pharmacists and healthcare providers: even a short conversation increases quit attempts.
• Online communities and peer support.

Preparing to quit: a step-by-step plan

1. Know your reasons

Write down why you want to stop: your health, your children, money, fitness, freedom. Keep the list somewhere you will see it.

2. Set a quit date

Choose a date within the next two weeks. Pick a time that is not unusually stressful, but do not wait for the “perfect” time; it rarely comes.

3. Get support and medicine

Contact a stop-smoking service, quitline, pharmacist or healthcare provider. Decide which medicine you will use and have it ready before your quit date.

4. Identify your triggers

For a few days before your quit date, note when and why you smoke. Plan what you will do instead in each situation.

5. Prepare your environment

Remove cigarettes, lighters and ashtrays from your home, car and workplace. Clean your clothes and car to remove the smell. Ask others not to smoke around you or offer you cigarettes.

6. Tell people

Tell family, friends and colleagues you are stopping and how they can help.

7. Plan rewards

Work out how much money you will save and plan something to spend it on.

Managing withdrawal symptoms

Withdrawal symptoms usually peak in the first week and improve over two to four weeks. Using stop-smoking medicine reduces them significantly. Common symptoms and tips:

• Cravings: usually last a few minutes. Use the “four Ds”: delay (wait a few minutes), deep breathing, drink water, and do something else.
• Irritability and anxiety: exercise, relaxation techniques and fast-acting NRT help.
• Difficulty concentrating: break tasks into smaller pieces and take short breaks.
• Increased appetite: have healthy snacks ready, drink water, and eat regular meals.
• Sleep problems: limit caffeine (nicotine speeds up caffeine breakdown, so the same coffee has a stronger effect after quitting), and remove patches at night if you have vivid dreams.
• Coughing: often temporary as the lungs clear. A persistent or worsening cough should be checked.
• Constipation and mouth ulcers: eat more fibre and drink plenty of fluids; these usually settle.
• Low mood: usually temporary. Seek help if it persists or is severe.

Coping with cravings and triggers

• After meals: get up from the table, brush your teeth or go for a short walk.
• With coffee or tea: change the routine, such as drinking it somewhere different or switching drinks for a while.
• With alcohol: alcohol is one of the most common reasons for relapse. Consider avoiding or reducing alcohol for the first few weeks.
• At work breaks: spend breaks with non-smokers, go for a walk or call a friend.
• When driving: remove the car lighter, keep gum or water in the car, and play music or podcasts.
• When stressed: use breathing techniques, physical activity or talk to someone.
• When bored: keep your hands busy with a stress ball, a puzzle or your phone.

Weight gain after quitting

Many people gain some weight after stopping smoking, on average around 4 to 5 kilograms over the first year, although some gain none and others gain more. This happens because nicotine slightly speeds up metabolism and suppresses appetite, and some people replace cigarettes with food. The health benefits of quitting vastly outweigh the risks of this modest weight gain.

To limit weight gain:

• Use stop-smoking medicine, which can delay weight gain.
• Plan healthy snacks such as fruit, vegetables, nuts and plain yoghurt.
• Drink water and avoid sugary drinks.
• Increase physical activity, which also reduces cravings.
• Focus on stopping smoking first; you can work on weight later if needed.

Slips and relapses

Most people make several attempts before they quit for good. A slip, smoking one or a few cigarettes, does not mean you have failed. What matters is what you do next:

• Do not think “I’ve blown it, so I might as well smoke.”
• Get rid of any remaining cigarettes.
• Think about what triggered the slip and plan for it next time.
• Keep using your stop-smoking medicine.
• Contact your support service.

If you do return to smoking, every attempt teaches you something. Many successful ex-smokers needed several tries. Try again as soon as you feel ready, with more support.

Quitting in pregnancy

Stopping smoking is one of the best things you can do for your baby. Smoking in pregnancy increases the risk of miscarriage, stillbirth, premature birth, low birth weight, sudden infant death and breathing problems in childhood. Stopping at any point in pregnancy helps, and the earlier the better.

• Behavioural support from specialist pregnancy stop-smoking services is highly effective.
• NRT is considered safer than smoking during pregnancy and is often recommended. Intermittent products (gum, lozenges, sprays) may be preferred, and patches should be removed at night.
• Varenicline, cytisine and bupropion are generally not recommended during pregnancy.
• Partners and family members who smoke should be encouraged to stop too, to protect the baby from second-hand smoke.

Talk to your midwife or healthcare provider about support available to you.

Quitting with mental health conditions

Smoking rates are much higher among people with mental health conditions, who often want to stop as much as anyone else. Stopping smoking does not worsen mental health; in fact, it often improves anxiety and depression. Some psychiatric medicines, such as clozapine and olanzapine, are affected by smoking, because smoke speeds up their breakdown. When you stop smoking, levels of these medicines can rise, so doses may need to be reduced. Tell your mental health team before you quit.

Quitting with heart or lung disease

Stopping smoking is the single most effective treatment for people with chronic obstructive pulmonary disease (COPD), and it dramatically reduces the risk of further heart attacks in people with heart disease. NRT and varenicline are safe for most people with heart disease. Specialist teams often have dedicated stop-smoking support.

Quitting before surgery

Smokers have higher rates of wound infection, poor wound healing, breathing complications and heart problems after surgery. Stopping as early as possible before an operation, ideally at least four to eight weeks, reduces these risks, but even stopping a day or two beforehand helps by reducing carbon monoxide levels. Use NRT in hospital to manage withdrawal.

Other forms of tobacco

Many people use tobacco in forms other than cigarettes, including hand-rolled tobacco, cigars, pipes, waterpipes (shisha or hookah), bidis, kreteks and smokeless tobacco such as chewing tobacco, gutka, paan with tobacco, snuff and snus. All carry serious health risks. Waterpipe smoking exposes users to large amounts of smoke and carbon monoxide in a single session. Smokeless tobacco causes mouth, throat and oesophageal cancer and is a major problem in South Asia. The same quitting principles, behavioural support and medicines, apply to all forms of tobacco.

Second-hand smoke and smoke-free homes

There is no safe level of exposure to second-hand smoke. It causes heart disease, lung cancer and stroke in adults, and in children it causes chest infections, asthma attacks, ear infections and sudden infant death. Making your home and car completely smoke-free protects your family, even before you quit. Smoking near an open window or in another room does not remove the risk.

A note for nurses and healthcare workers

Nurses have more contact with patients than almost any other health professional, which makes them extremely well placed to help people stop smoking. The “Very Brief Advice” approach, Ask, Advise, Act, takes less than a minute: ask about smoking, advise that the best way to stop is with support and medicine, and act by offering a referral or prescription. Recording smoking status, offering NRT to hospital inpatients to manage withdrawal, and following up are simple actions with big impact. Nurses who smoke themselves are encouraged to seek support: many health services offer dedicated help for staff, and quitting protects both your own health and your role as a trusted health messenger.

Common myths about quitting smoking

• “Smoking relieves my stress.” Much of that relief is ending nicotine withdrawal. Ex-smokers typically report lower stress levels after the first few weeks.
• “It’s too late for me to benefit.” Stopping at any age improves health and life expectancy.
• “Nicotine causes cancer.” Nicotine is addictive, but most harm from smoking comes from the tar and other chemicals in smoke.
• “NRT is as bad as smoking.” NRT is far safer and doubles your chance of quitting.
• “Light or menthol cigarettes are safer.” They are not. People often inhale more deeply to compensate.
• “Cutting down is just as good.” Even a few cigarettes a day significantly increase heart disease risk. Stopping completely gives the greatest benefit.

Your first 30 days: what to expect

Days 1 to 3

These are often the hardest days. Nicotine leaves your body within about 72 hours, and withdrawal symptoms usually peak during this time. Cravings may be frequent. Use your stop-smoking medicine exactly as planned, keep busy, drink plenty of water, avoid alcohol and situations where you would normally smoke, and contact your support service or quitline if you are struggling. Count each smoke-free hour as a win.

Days 4 to 7

Physical withdrawal begins to ease, but habits and triggers remain strong. You may feel tired, irritable or emotional. Many people notice they are breathing more easily and their sense of taste and smell is improving. Keep using fast-acting NRT or your other medicine for cravings, and keep reminding yourself of your reasons for quitting.

Week 2

Cravings are usually less frequent, though they can still be intense when triggered. Your circulation is improving. This is a good time to start or increase physical activity, which reduces cravings and helps with mood and weight.

Weeks 3 and 4

Most people find withdrawal symptoms have largely settled. The risk now is complacency: thinking “one won’t hurt”. Remember that for most ex-smokers, one cigarette leads back to regular smoking. Stay alert to high-risk situations such as parties, alcohol, arguments and stressful events, and keep your plan in place. Reward yourself with some of the money you have saved.

After the first month

Continue your medicine for the full course, usually at least 8 to 12 weeks, even if you feel you no longer need it, because stopping too early increases relapse risk. Occasional cravings may appear unexpectedly months later. They pass, and they become rarer over time.

Calculating what you will save

Money is a powerful motivator. Multiply the number of packs you smoke each week by the price of a pack, then multiply by 52 to see the yearly cost. For many people, especially in countries with high tobacco taxes, this amounts to a large sum each year, enough for a holiday, school fees, a significant household purchase or savings. Some people put the money they would have spent on cigarettes into a jar or separate account each day, so they can see it grow. Even in countries where cigarettes are cheap, the money adds up over years, and the costs of smoking-related illness, time off work and medical care are far greater.

Helping someone you care about to quit

If someone close to you smokes, you may desperately want them to stop. Nagging, criticising or lecturing rarely works and can make people defensive. More effective approaches include:

• Expressing care and concern, rather than judgement: “I love you and I worry about your health.”
• Asking whether they have thought about stopping and what would help.
• Sharing information about support services and medicines, which many people do not know about.
• Offering practical help, such as going to appointments with them, keeping the home smoke-free, or doing an activity together when cravings strike.
• Being patient with irritability in the first weeks.
• Celebrating milestones: one day, one week, one month, one year.
• If they slip, encouraging them to try again rather than expressing disappointment.

If you smoke too, consider quitting together. Couples and friends who quit together can support each other.

Young people and smoking

Most adult smokers started before the age of 18, when the developing brain is especially sensitive to nicotine addiction. Young people who smoke or vape can become dependent quickly. Many young people want to stop and find it harder than they expected. Support designed for young people, including school-based programmes, text and app-based support, and advice from school nurses and healthcare providers, can help. NRT can be used by adolescents in many countries under guidance. Parents can help by not smoking themselves, keeping homes smoke-free, talking openly without lecturing, and supporting quit attempts.

Tobacco control around the world

The WHO Framework Convention on Tobacco Control, a global treaty ratified by most countries, commits governments to measures that reduce tobacco use. The WHO’s “MPOWER” package summarises the most effective policies: monitoring tobacco use, protecting people from smoke through smoke-free laws, offering help to quit, warning about the dangers through graphic health warnings and plain packaging, enforcing bans on tobacco advertising and sponsorship, and raising taxes on tobacco. Higher tobacco prices are one of the most effective ways to reduce smoking, especially among young people and those on lower incomes. Smoking rates have fallen in many countries as a result, but tobacco use is still high in parts of Asia, Eastern Europe, the Middle East and Africa, and the tobacco industry continues to target new markets. Every individual who quits is part of this larger public health success.

Staying smoke-free for life

Long-term success depends on building a new identity as a non-smoker. People who stay smoke-free often describe a shift from “I am trying not to smoke” to “I don’t smoke”. Helpful habits include:

• Never allowing yourself “just one”, even years later.
• Recognising high-risk situations, such as heavy drinking, grief, work stress or being around smokers, and having a plan for them.
• Keeping a fast-acting NRT product available for unexpected strong cravings in the first year.
• Continuing regular exercise and stress management.
• Reminding yourself of the benefits you have gained, such as easier breathing, more money and better health.
• Helping others to quit, which reinforces your own commitment.

Questions to ask a pharmacist or healthcare provider

• Which stop-smoking medicine is best for me, and how do I use it properly?
• Should I use combination NRT, and what strengths?
• Is varenicline or cytisine available here, and is it suitable for me?
• Is there a local stop-smoking service, quitline or app you recommend?
• Will stopping smoking affect any of my current medicines?
• What should I do if I have a slip?
• How can I limit weight gain?

Smoking and your appearance, fertility and sexual health

For many people, especially younger smokers, long-term disease feels distant. The more immediate effects of smoking can be powerful motivators to stop. Smoking reduces blood flow to the skin, breaks down collagen and speeds up wrinkling, particularly around the mouth and eyes. It stains teeth and fingers, causes bad breath and increases gum disease and tooth loss. It reduces fertility in both women and men, increases the risk of miscarriage and ectopic pregnancy, and can bring forward menopause. In men, smoking damages the blood vessels needed for erections and is a significant cause of erectile dysfunction. Many of these effects improve after quitting: skin tone and circulation improve, gum health can recover, and fertility and sexual function often get better within months.

Smoking, exercise and fitness

Carbon monoxide in cigarette smoke binds to red blood cells and reduces the amount of oxygen they carry, which is why smokers become breathless more quickly during exercise. Within weeks of stopping, many people notice they can walk further, climb stairs more easily and recover faster after exercise. Physical activity is also one of the best tools for quitting: even a ten-minute brisk walk can reduce cravings and withdrawal symptoms for some time afterwards. Building exercise into your quit plan helps your body recover, lifts your mood, limits weight gain and gives you a new, healthy routine to replace smoking.

Making your quit plan

Write down a simple plan and keep it where you can see it:

• My quit date: …
• My top three reasons for quitting: …
• My stop-smoking medicine and dose: …
• My support: stop-smoking service, quitline, app, friend or family member …
• My three biggest triggers and what I will do instead: …
• What I will do if I slip: …
• How I will reward myself: …

Having this written down, and sharing it with someone who supports you, makes it far more likely you will follow through when cravings test your resolve.

Quitting when you live with other smokers

Living with someone who smokes makes quitting harder, because cigarettes, smell and social cues are all around you. Ask household members not to smoke indoors or offer you cigarettes, and to keep their tobacco out of sight. Agree that your home and car will be smoke-free. Spend more time in places where smoking is not allowed during the first weeks. If your partner or housemate is not ready to quit, ask them to respect your attempt; many people find their own motivation once they see someone close to them succeed. Quitting together, with each person using medicine and support, roughly doubles the encouragement available to both.

Celebrating milestones

Mark each milestone: the first smoke-free day, week, month, three months and year. Notice the changes in your breathing, energy, sense of smell and bank balance. Every day without smoking is good for your body, whatever happened before.

Quitting at older ages

Some older smokers believe it is too late for stopping to make a difference. The evidence says otherwise. People who stop in their 60s and 70s still gain years of life on average, breathe more easily, reduce their risk of heart attack and stroke, recover better from illness and surgery, and lower the risk of complications from conditions such as diabetes and osteoporosis. Stop-smoking medicines are suitable for most older adults, and support services welcome people of every age.

Frequently asked questions

How long do cravings last?

Individual cravings usually pass within a few minutes. Withdrawal symptoms generally improve over two to four weeks, though occasional cravings can occur for months, often triggered by specific situations.

Is it better to quit suddenly or cut down?

Both approaches can work. Stopping on a set quit date is slightly more effective on average, but cutting down with NRT is a good option for people who prefer it.

Can I use NRT and still smoke?

Using NRT while cutting down is safe and can help you move towards quitting.

Will I gain weight?

Many people gain some weight, but it can be limited with healthy eating and activity, and the health benefits of quitting far outweigh it.

Are heated tobacco products a safe alternative?

Heated tobacco products still contain tobacco and toxic chemicals. They are not approved quitting aids, and the best choice is to stop all tobacco use.

How many times do people try before quitting?

It varies widely, but many successful ex-smokers made several attempts. Each attempt increases your chance of eventual success.

But what if I have tried everything and still cannot quit?

Often, “everything” has meant trying willpower alone, using a single type of NRT at too low a dose, or stopping medicine too early. Ask a stop-smoking service or healthcare provider about combination NRT at a proper dose, varenicline or cytisine, or switching completely to a regulated vape where this is supported. Combine medicine with weekly support for at least the first month. Look closely at what caused previous relapses, especially alcohol and stress, and plan for them. Quitting is a skill that improves with practice. You have not failed; you are learning how to succeed.

Related: How to quit smoking: methods that work · COPD: the complete guide

Sources: World Health Organization (tobacco fact sheet, WHO Framework Convention on Tobacco Control, clinical treatment guideline for tobacco cessation), Cochrane Tobacco Addiction Group reviews, US Surgeon General reports on smoking cessation, National Institute for Health and Care Excellence (NICE) tobacco guidance, EAGLES trial (varenicline safety), Doll and Peto British Doctors Study.