September 30, 2026
Quitting smoking: what happens, day by day
IrisThe article as a film – 11 minutes, English narration. Download.
5.4 percent of Sweden’s population smoke daily (Public Health Agency of Sweden, 2024) [1]. The question they are looking for an answer to is concrete: what happens in the body, and when? Here is the timeline, with the sources written out.
The question nobody answers
1177 Vårdguiden gives three time windows. Within one day: blood pressure and pulse fall, the carbon monoxide level drops, nicotine is at zero after 24 hours. Within six months: lungs and blood circulation work better, the cilia in the airways recover. One year later: the immune system is stronger and the risk of heart attack has fallen [2].
The same broad phases appear at the Public Health Agency, the National Board of Health and Welfare and the Quit Smoking Line. None of them goes down to the day level.
Anyone who instead searches for “hour by hour” ends up with those who sell nicotine. IQOS, the Philip Morris product line, has a Swedish article headed “What happens in the body when you stop smoking?” with the button “Are you ready for an alternative to cigarettes?” [3]. Snusforumet answers that it takes “between one and two weeks for the nicotine to leave the body completely” [4]. The half-life of nicotine is two hours. Cotinine, the breakdown product that is measured, has a half-life of about 16 hours and reflects the last three to four days [5].
We have nothing to sell. That is the premise for the rest of this text.
The timeline
First 24 hours
20 minutes. Pulse and blood pressure begin to fall (WHO [6], NHS [7], 1177 [2]).
8 hours. The carbon monoxide in the blood is halved and oxygen uptake improves (NHS [7]).
12 hours. Carbon monoxide is down to a normal level (WHO [6]).
24 hours. The nicotine in the blood is at zero (1177 [2]).
First weeks
48 hours. Taste and smell begin to come back, the lungs clear mucus (NHS [7]).
3 days. Withdrawal is at its worst (peer-reviewed review [8]).
2–12 weeks. Blood circulation and lung function improve, the skin becomes less grey (WHO [6], 1177 [2]).
Months and years
3–9 months. Cough and breathlessness decrease. Lung function has improved by up to 10 percent (NHS [7]).
1 year. The risk of coronary heart disease is roughly halved (WHO [6], NHS [7], the Swedish Cancer Society [9]).
5–15 years. The risk of stroke approaches that of a non-smoker (WHO [6]). After 15 years the risk of stroke and heart attack has fallen to a level close to a non-smoker’s (1177 [2]).
10 years. The risk of dying of lung cancer is halved (WHO [6], NHS [7], the Swedish Cancer Society [9]).
15 years. The risk of coronary heart disease is the same as for a person who has never smoked (WHO [6]).
All the numbers are averages for groups and relative risks against those who carry on smoking, not promises to an individual. None of them is medical advice.
Withdrawal
The symptoms start 4–24 hours after the stop, are at their worst around the third day and taper off over the following three to four weeks [8].
1177 does not say the same thing on two of its own pages. On “Help to quit smoking” it says that the withdrawal symptoms usually disappear “after one to three weeks” [2]. On “Medicines to quit smoking” it says they “usually disappear one to two weeks after you have stopped smoking” [10]. Anyone who copies 1177 picks one of the numbers without knowing the other exists.
Cravings are measured in two different orders of magnitude. 1177 writes “20–30 seconds” [2]. The Quit Smoking Line writes “at its worst for a couple of minutes” [11]. Seconds for the single urge, minutes for the continuous craving.
The Quit Smoking Line writes that the symptoms “usually are gone within a month” [11]. The Swedish Cancer Society writes that most people feel better three to four weeks after stopping, and that the withdrawal symptoms are gone or almost gone after about three months [9].
Weight is the part of withdrawal that most people worry about, and it has been measured. In a meta-analysis of 62 studies (BMJ, 2012), untreated smokers gained 1.12 kg after one month, 2.26 kg after two, 2.85 kg after three, 4.23 kg after six and 4.67 kg after twelve. After one year, 16 percent had lost weight and 37 percent had gained less than five kilos [12]. The big gain is not the usual case.
Support is available at the health centre and from the Quit Smoking Line: 020-84 00 00, Monday–Thursday 10–18, Friday 10–15, by phone or chat, free of charge. The line has existed since 1998 and is run by the Centre for Epidemiology and Community Medicine within Region Stockholm [11][13]. That is the only referral this text makes. What works for the other nicotine products is set out in How to quit.
The chance of succeeding depends on the support. Quitting on your own gives a 2–3 percent chance of being smoke-free one year later, according to Psychologists against Tobacco; for the truly motivated, 7–10 percent [14][15]. Tobaksfakta states that about 30 percent of those who get support from a trained tobacco cessation counsellor are smoke-free after one year [16], and the Quit Smoking Line’s own figure is about 35 percent self-reported tobacco-free after twelve months [13]. The word self-reported is there on purpose: it is the line’s own follow-up.
What does not add up
These sentences stand on hundreds of Swedish pages. No Swedish authority and not the WHO stands behind them.
“After 8 hours the carbon monoxide is normal.” The WHO says 12 hours. The NHS says halved at 8 hours and normal only after 48.
“After 24 hours the risk of heart attack falls.” No source. The CDC writes that the risk of coronary heart disease falls sharply one to two years after the stop [17].
“After 48 hours the nerve endings grow back.” No current authority. The NHS says that taste and smell improve.
“After 72 hours the nicotine is completely gone.” 1177 says 24 hours. Cotinine can be measured for three to four days.
“After 72 hours lung capacity increases.” No source. The NHS says the bronchi relax and energy comes back.
“After 2–3 months lung function increases by 30 percent.” The NHS says up to 10 percent, and only after 3–9 months.
“After 5 years the stroke risk is like a non-smoker’s.” The WHO says it takes 5–15 years.
“After 1 year the lungs are clean.” No source. The sources talk about better lung function, never about healed lungs.
The errors spread into serious texts. The Swedish Cancer Society’s page about quitting smoking opens with “after 24 hours the risk of heart attack has fallen and after 48 hours the nicotine is out of the body” [9], while the timeline further down says twelve hours for the carbon monoxide and does not mention nicotine at all.
The same kind of copied error exists in the lists of what a cigarette contains: a cigarette is said to contain 1,000 substances, the smoke contains over 7,000, and the 7,000 are mixed up with the roughly 600 that are added on purpose. We have been through both, in 1,000 substances in a cigarette and added substances.
What does hold, however, are the long numbers. After ten years the risk of dying of lung cancer is halved (WHO, NHS). After fifteen years the risk of coronary heart disease is the same as for someone who has never smoked (WHO). None of the sources says the lungs become like new.
Newer texts, releases and songs from the site are under News.
Sources
- Public Health Agency of Sweden, Living habits — Results for the follow-up of public health policy target area 6 (article number 24242, updated 28 March 2025). Share who smoke daily in 2024: 5.4 percent; the fall 2006–2024: from 14 to 5 percent.
https://www.folkhalsomyndigheten.se/pubreader/pdfview/121077?browserprint=1 - 1177 Vårdguiden, Help to quit smoking. The timeline within one day, six months and one year; cravings “20–30 seconds”; withdrawal symptoms “after one to three weeks”; medicines double the chance; phone number to the Quit Smoking Line.
https://www.1177.se/liv–halsa/tobak-och-alkohol/tobak/hjalp-att-sluta-roka/ - IQOS (Philip Morris), Quit smoking — “What happens in the body when you stop smoking?”, published 13 June 2025. The article is surrounded by buy buttons and by the line “Our nicotine and tobacco products are not aids for quitting smoking”.
https://se.iqos.com/sv/nyheter/sluta-r%C3%B6ka - Snusforumet, Nicotine — answers to the most common questions, updated 7 August 2025. “It usually takes between one and two weeks for the nicotine to leave the body completely.”
https://snusforumet.se/fakta/nikotin - Benowitz NL, Nicotine Chemistry, Metabolism, Kinetics and Biomarkers. The half-life of nicotine in plasma about 2 hours; the half-life of cotinine about 16 hours, which means cotinine reflects exposure over the last 3–4 days.
https://pmc.ncbi.nlm.nih.gov/articles/PMC2953858/ - WHO, Tobacco: health benefits of smoking cessation (25 February 2020). 20 minutes; 12 hours; 2–12 weeks; 1 year; stroke 5–15 years; 10 years; 15 years.
https://www.who.int/news-room/questions-and-answers/item/tobacco-health-benefits-of-smoking-cessation - NHS, Quit smoking. 20 minutes; 8 hours (halved carbon monoxide); 48 hours; 72 hours; 2–12 weeks; 3–9 months (up to 10 percent better lung function); 1 year; 10 years.
https://www.nhs.uk/better-health/quit-smoking/ - Nicotine Withdrawal (peer-reviewed review). “An aversive abstinence syndrome manifests 4–24 h following cessation […] Symptoms peak on approximately the 3rd day and taper off over the course of the following 3–4 weeks.”
https://pmc.ncbi.nlm.nih.gov/articles/PMC4542051/ - Swedish Cancer Society (Cancerfonden), Quit smoking (revised 24 May 2024). 20 minutes; 12 hours; 2–12 weeks; 1 year; 5 years; 10 years; three to four weeks; about three months. The introduction contains the two sentences about 24 hours and 48 hours.
https://www.cancerfonden.se/minska-risken/tobak/rokning/sluta-roka - 1177 Vårdguiden, Medicines to quit smoking (last updated 3 February 2025, reviewed by Rosaria Galanti, epidemiologist and tobacco researcher at Karolinska Institutet). “The withdrawal symptoms usually disappear one to two weeks after you have stopped smoking.”
https://www.1177.se/undersokning-behandling/behandling-med-lakemedel/lakemedel-utifran-diagnos/lakemedel-mot-rokning/ - The Quit Smoking Line, When you have stopped and the home page. Cravings “at their worst for a couple of minutes”; “the symptoms usually are gone within a month”; phone 020-84 00 00, Monday–Thursday 10–18, Friday 10–15, chat.
https://www.slutarokalinjen.se/att-sluta/nar-du-har-slutat/ - Aubin HJ, Farley A, Lycett D, Lahmek P, Aveyard P, “Weight gain in smokers after quitting cigarettes: meta-analysis”, BMJ 2012;345:e4439. 62 studies; +1.12 kg after 1 month, +2.26 after 2, +2.85 after 3, +4.23 after 6, +4.67 after 12; at 12 months 16 percent had lost weight and 37 percent had gained less than 5 kg.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3393785/ (same article; the BMJ’s own address, https://www.bmj.com/content/345/bmj.e4439, answers 403 to scripts but opens in a browser) - The Quit Smoking Line, About us. Active since 1998, run by the Centre for Epidemiology and Community Medicine (CES) within Region Stockholm, mainly financed by the Ministry of Health and Social Affairs, national mandate, over 150,000 calls, “about 35 percent self-reported tobacco-free after twelve months”.
https://www.slutarokalinjen.se/om-oss/ - Psychologists against Tobacco, Methods for quitting smoking and snus. “Only 2-3 people out of 100 are smoke-free one year after” an attempt on one’s own; “One in three is smoke-free one year after calling” the Quit Smoking Line.
https://www.psykologermottobak.org/vad-vill-du-g%C3%B6ra/metoder-f%C3%B6r-r%C3%B6k-och-snusstopp - Psychologists against Tobacco, Methods for counselling and tobacco cessation. The New Year’s resolution 2–3 percent; “for the truly motivated one can count on 7-10 percent (Nohlert)”.
https://www.psykologermottobak.org/metoder-f%C3%B6r-r%C3%A5dgivning-och-tobaksavv%C3%A4njning - Tobaksfakta, Professional tobacco cessation counsellors are important for quitting (25 December 2022). “Qualified counselling and concrete support from a tobacco cessation counsellor: 30 percent smoke-free after one year.” Tobaksfakta’s background page Methods and medicines for tobacco cessation in turn refers to the National Institute of Public Health’s publication Tobacco and cessation.
https://tobaksfakta.se/professionella-tobaksavvanjare-har-stor-betydelse-for-tobaksstopp/ - CDC, Benefits of Quitting Smoking (15 May 2024). “Reduces the risk of coronary heart disease with risk falling sharply 1-2 years after cessation.”
https://www.cdc.gov/tobacco/about/benefits-of-quitting.html
All links opened on 30 September 2026.
Idea and selection: Pero · biological intelligence
Text: Iris · artificial intelligence
Number check: Aurora · artificial intelligence
This article is a translation of the Swedish original: “Vad händer när man slutar röka, dag för dag” — https://fimpanu.com/vad-hander-nar-man-slutar-roka-dag-for-dag/