When a surgeon or an anaesthetist asks whether you smoke, they are not making conversation and they are not judging you. They are estimating risk, because smoking changes several things that surgery depends on: how much oxygen your blood can carry, how well a wound closes, how your airways behave under anaesthesia, and how likely you are to develop a chest infection afterwards. Smokers have measurably higher rates of wound infection, poor healing, breathing complications, and longer hospital stays. An operation is one of the few moments where the difference is immediate and concrete rather than statistical and distant.
The useful thing is that the clock starts working for you very quickly.
Within about twelve to twenty-four hours, carbon monoxide clears from your bloodstream. Carbon monoxide takes up space on your red blood cells that oxygen should be occupying, so clearing it means more oxygen reaching tissue — including the tissue a surgeon is about to cut and expects to heal. Nicotine's effect of narrowing small blood vessels also eases in roughly the same window, which matters for the same reason.
Within a couple of days to a couple of weeks, your airways become less reactive and start clearing themselves properly again. This is the phase where some people cough more, not less, which is your lungs doing overdue housekeeping rather than a sign of harm.
From around four weeks, the benefit that surgical teams care about most starts to show clearly: lower rates of wound complications and respiratory problems. The effect keeps growing with more time, which is why many surgeons suggest six to eight weeks where the schedule allows it.
There is an old idea, still repeated occasionally, that quitting shortly before an operation is worse than not quitting at all because of the increase in coughing and mucus. The research has not supported this. Stopping is beneficial at essentially any point before surgery, and stopping the day before is better than not stopping. If your date is next week, quit anyway.
A few practical points. Tell the anaesthetist the truth about how much you smoke, including if you started again recently — the plan they make is safer when the number is accurate, and they have heard it all before. Ask about nicotine replacement, because it is usually permitted and often actively encouraged around surgery; it addresses the withdrawal without the carbon monoxide, tar, and vessel-narrowing that cause the surgical problems. If you use a vape, ask specifically rather than assuming, since policies differ.
And there is an opportunity hidden in this that is easy to miss. A hospital stay is an enforced smoke-free stretch during which you are busy, monitored, and away from every one of your usual cues. People routinely spend that stretch counting down to the first cigarette after discharge, which wastes the hardest part of a quit that has already been done for them. If you go in having decided that the operation is the quit date rather than an interruption, you come out several days in with the worst of the withdrawal behind you.
A surprising number of long-term ex-smokers date their quit to an operation. A real deadline, an obvious reason, and a few days of forced abstinence turn out to be a better combination than most planned attempts ever get.