Fig. 14Stage 5, After
after quitting, the NHS says risk of heart attack will have halved compared with a smoker's.
SourceNHS Better Health, Quit smoking2026
What happens to the body after you quit smoking, hour by hour and year by year
CDC and the NHS publish time points for pulse, carbon monoxide, lungs, heart attack, stroke and cancer risk. Here they are as the sources state them, with their differences.
People often ask how soon quitting does anything useful. Two public health agencies answer with dated milestones. The NHS says that after 1 year of not smoking, your risk of heart attack will have halved compared with a smoker's. The CDC places a sharp fall in heart attack risk at 1 to 2 years. This page sets out each agency's time points as they state them, explains why the two lists differ in places, and notes what the figures do and do not mean.
The first minutes, hours and days
The earliest changes involve the pulse, nicotine and carbon monoxide, a gas in cigarette smoke that reduces the oxygen your blood can carry. The NHS Better Health timeline lists these steps: after 20 minutes, pulse rate is already starting to return to normal; after 8 hours, oxygen levels are recovering and the harmful carbon monoxide level in the blood will have reduced by half; after 48 hours, carbon monoxide levels have dropped to that of a non-smoker, and the senses of taste and smell are improving; after 72 hours, breathing may feel easier because the bronchial tubes have started to relax.
The CDC's Benefits of Quitting Smoking page gives a coarser version. It says heart rate drops within minutes, nicotine level in the blood drops to zero at 24 hours, and carbon monoxide level in the blood drops to the level of someone who does not smoke after several days. The NHS says 48 hours and the CDC says several days. The two are not in conflict so much as stated at different precision, and individual results vary.
These first days are also when withdrawal is usually at its strongest. Our withdrawal timeline covers cravings, irritability and sleep, which can run alongside the improvements above.
Weeks and months
The NHS reports that after 2 to 12 weeks, circulation will have improved so that blood pumps to the heart and muscles much better. After 3 to 9 months, it says coughs, wheezing or breathing problems will be improving as lung function increases by up to 10%. The CDC says coughing and shortness of breath decrease between 1 and 12 months.
The NHS adds a separate point on mood. On its benefits page it states that it can take as little as 6 weeks to start feeling the mental health benefits of stopping smoking. For more on that, see quitting and mental health.
Years later: heart disease, stroke and cancer
The longer milestones are where the CDC list is most detailed. The table below reproduces its time points. The CDC notes that, in its list, risks described as dropping or decreasing refer to the benefits of cessation compared with continued smoking.
| Time since last cigarette | What the CDC says |
|---|---|
| Minutes | Heart rate drops. |
| 24 hours | Nicotine level in the blood drops to zero. |
| Several days | Carbon monoxide level in the blood drops to level of someone who does not smoke. |
| 1 to 12 months | Coughing and shortness of breath decrease. |
| 1 to 2 years | Risk of heart attack drops sharply. |
| 3 to 6 years | Added risk of coronary heart disease drops by half. |
| 5 to 10 years | Added risk of cancers of the mouth, throat, and voice box drops by half. Risk of stroke decreases. |
| 10 years | Added risk of lung cancer drops by half after 10 to 15 years. Risk of cancers of the bladder, esophagus, and kidney decreases. |
| 15 years | Risk of coronary heart disease drops to close to that of someone who does not smoke. |
| 20 years | Risk of cancers of the mouth, throat, and voice box drops to close to that of someone who does not smoke. Risk of pancreatic cancer drops to close to that of someone who does not smoke. Added risk of cervical cancer drops by about half. |
The NHS gives overlapping figures on its benefits page: after 1 year, risk of heart attack halves compared with a smoker's; after 10 years, risk of death from lung cancer falls to half that of a smoker; after 15 years, risk of heart attack falls to the same as someone who has never smoked. The CDC speaks of coronary heart disease at 15 years and the NHS speaks of heart attack, so the two should not be treated as a single measurement. On stroke, the CDC also says quitting reduces the risk of disease and death from stroke, with risk approaching that of never smokers after cessation. Our page on smoking and stroke risk covers the stroke evidence in more detail.
How to read these figures
All of these are population-level comparisons between people who quit and people who keep smoking. They do not promise a specific outcome for one person, and they depend on how long and how heavily someone smoked. The CDC and the 2020 US Surgeon General's report, Smoking Cessation, also say quitting is beneficial at any age and can add as much as 10 years to life expectancy, while the CDC notes that quitting earlier yields greater benefit.
Many of these gains build over years, which is why a slip is better treated as a setback to recover from, a point developed in relapse and slips. A person with heart disease, lung disease or cancer, or one who is pregnant, should ask their clinician how to quit safely, since some conditions and medicines change the plan.
Frequently asked questions
How long after quitting does carbon monoxide leave the blood?
The NHS says carbon monoxide has reduced by half after 8 hours and dropped to a non-smoker's level after 48 hours. The CDC says it drops to the level of someone who does not smoke after several days.
When does the risk of lung cancer fall?
The CDC says the added risk of lung cancer drops by half after 10 to 15 years, and the NHS says the risk of death from lung cancer falls to half that of a smoker after 10 years. Both compare ex-smokers with those who continue to smoke.
Is it too late to quit after many years of smoking?
The CDC states that quitting smoking has health benefits at any age, no matter how long or how much you have smoked. The NHS likewise says it is never too late.
The short version
Pulse and carbon monoxide begin to recover within hours or days, and the NHS puts the halving of heart attack risk at 1 year. Cancer and coronary heart disease milestones run from 3 years to 20 years in the CDC's list. Figures differ slightly between agencies, so read them as ranges. Ask a clinician or pharmacist for help if you have a heart or lung condition, are pregnant, or take other medicines.