CigCountWhen you quit smoking, your body starts to change almost right away: according to WHO, within 20 minutes your heart rate and blood pressure drop. Other changes arrive over hours, weeks and years. The timings below are the ones WHO, the CDC and the NHS publish (and, as added context, the American Cancer Society), and they can vary from person to person.
What happens in the first 48 hours?
- 20 minutes. According to WHO, your heart rate and blood pressure drop. The NHS puts it differently: your pulse rate is already starting to return to normal.
- 12 hours. According to WHO, the carbon monoxide level in your blood drops to normal.
- 24 hours. According to the CDC, the nicotine level in your blood drops to zero.
- 48 hours. According to the NHS, your carbon monoxide levels have dropped to that of a non-smoker.
When does nicotine in your blood drop? Of WHO, the CDC and the NHS, only the CDC gives a timing (24 hours); WHO and the NHS don’t mention it on their pages.
Notice that carbon monoxide shows up twice: WHO says 12 hours and the NHS says 48. The sources don’t agree on the timing, so we don’t blend or average them. Each number stays with its source.
When do your lungs start to improve?
There isn’t a single timing, because the sources describe improvements at different stages:
- Between 2 and 12 weeks. According to WHO, your circulation improves and your lung function increases.
- Between 3 and 9 months. According to the NHS, coughs, wheezing and breathing problems improve as your lung function increases by up to 10%.
Nicotine withdrawal symptoms are a separate topic, and we cover them in nicotine withdrawal symptoms.
When does your heart attack risk go down?
At one year, two sources measure different things, so it helps not to mix them up:
- According to the NHS, your risk of heart attack has halved compared with a smoker’s.
- According to WHO, your risk of coronary heart disease is about half that of a smoker’s.
One is about heart attack and the other about coronary heart disease, so they aren’t the same figure. Further out, according to WHO, at 15 years the risk of coronary heart disease is that of a nonsmoker.
What about cancer risk?
- 5 to 10 years. As added context, the American Cancer Society says your risk of cancers of the mouth, throat and voice box (larynx) is cut in half.
- 10 years. According to WHO, your risk of lung cancer falls to about half that of a smoker.
The CDC also says that quitting smoking reduces the risk of 12 different cancers.
Is it worth quitting after many years of smoking?
Yes. According to the CDC, even people who have smoked for many years or have smoked heavily will benefit from quitting.
Which of the app’s milestones aren’t in this article?
CigCount shows 14 health milestones, each with its source. This article covers nine of them. The other five (8 hours, 72 hours, 28 days, 1 to 9 months and 5 years) and the direct source for all 14 are on the health sources page.
How current are these sources?
Health figures get reviewed over time, so it helps to know how current these sources are. The WHO page we used shows February 25, 2020. The CDC page shows May 15, 2024, with no label saying whether that is a publication or a review date. The NHS page shows no date, and the American Cancer Society page says it was last revised on May 23, 2025. We checked them on October 22, 2026. If any of them changes, this article should be updated.
How CigCount keeps you company
CigCount is an app that keeps you company, not a treatment. It shows your health milestones with their sources: for free you see the latest one you reached and the next one, and with Premium you get the full timeline with the detail of each one.
Milestones count from your last cigarette. If you’re cutting down, the app shows them as what’s ahead once you reach zero; if you’re curious about that path, you can read cut down or quit cold turkey. And if you smoke a cigarette, the timings count from that last cigarette, while your Day N keeps adding up.
If you’d like support to quit, talk to a health professional or to your local quitline.