Day 4 after quitting smokingYour coffee got stronger

By Yevhenii, who smoked for 26 years · Updated 30 Oct 2026 · 2 min read

In shortWithout smoke, the liver enzyme that clears caffeine slows down, so your usual coffee now hits harder. Jitters and poor sleep may be partly too much caffeine. Cutting it by about half and stopping before noon is in your hands.

What's happening in your body

Tobacco smoke switches on a liver enzyme called CYP1A2, the same one that breaks down caffeine. Smokers clear caffeine much faster than other people, which is one reason they tend to drink more coffee. Once the smoke stops, the enzyme's activity falls by half about every forty hours. By now the same cups leave considerably more caffeine in your blood than they did last week.

What to expect

Jitters, a racing mind, trouble falling asleep, a faster pulse after the second cup, sometimes a tight, anxious feeling in the chest or stomach. It is easy to file all of this under withdrawal, and part of it is. But part of it is simply an overdose of your usual coffee. In the study that measured it, caffeine was cleared about a third more slowly once smoking stopped, and the change settled within about a week.

So the same three cups now act more like four or five. The good news is that this part is entirely in your hands, and it responds within days.

Try this

Cut your caffeine by about half and have the last cup before noon. Tea, cola and energy drinks count too.

What else you could do

Keep it that way for two weeks and see what happens to your evenings. While you are at it, think about the coffee itself. It is one of the triggers most often logged in this app, because the hand goes for a cigarette when there is a cup beside it. So for the first weeks it makes sense not only to cut the dose but to break the pair. Swap the morning cup for tea, chicory or plain water, use a different mug, drink it somewhere else. Keep the break itself; just let the drink in it be a different one.

Sources. Faber MS, Fuhr U. Time response of cytochrome P450 1A2 activity on cessation of heavy smoking. Clin Pharmacol Ther, 2004. Benowitz NL, Hall SM, Modin G. Persistent increase in caffeine concentrations in people who stop smoking. BMJ, 1989.