Last updated: October 2026
Caffeine usually kicks in within 15 to 45 minutes and peaks in your blood around 30 to 60 minutes after a drink. Its half-life is roughly 3 to 6 hours in healthy adults, so about a quarter of a coffee can still be in your system 10 or more hours later. Stopping by early afternoon helps protect your sleep.
Below: an hour-by-hour timeline, what speeds caffeine up or slows it down, how much is in UK drinks, when to stop for good sleep, safe amounts and what happens when you cut down.
Caffeine timeline: what happens hour by hour
Caffeine is absorbed quickly and almost completely from the gut. In one study, a dose taken as a drink reached its peak in the blood after about 30 minutes, and in another, coffee and cola both peaked at around 40 minutes. Capsules were slower, at just over an hour. Here’s a typical picture for one coffee in a healthy adult:
| Time after your coffee | What’s happening |
|---|---|
| 0 to 15 minutes | Caffeine starts moving from your stomach and gut into your blood |
| 15 to 45 minutes | Most people start to feel more alert as levels climb |
| 30 to 60 minutes | Peak blood level for most drinks (up to 2 hours for some people, or with capsules) |
| 1 to 4 hours | Effects such as a small rise in blood pressure peak at 1 to 2 hours and can last more than 4 hours |
| 3 to 6 hours | About half the caffeine has been cleared (one half-life) |
| 6 to 12 hours | About a quarter is left, enough to affect sleep in many people |
| 24 hours | Only a small amount remains for most people |
The buzz often fades before the caffeine does, so you can feel flat mid-afternoon and still struggle to drop off at night. For the dip itself, see why coffee crashes happen and our guide to the afternoon slump.
What is caffeine’s half-life?
Half-life is the time it takes your body to clear half of the caffeine you’ve had. For most healthy adults it’s about 3 to 6 hours, with around 5 hours a fair middle figure. It varies a lot: in one small study of healthy young men, it ranged from 2.7 to 9.9 hours.
Your liver does almost all the work. One enzyme, called CYP1A2, handles about 95% of the caffeine you drink, and genetic differences in it are a big reason why one person sleeps fine after an evening espresso while another is wired from a lunchtime tea. Here’s how a single 100mg coffee (about one cup of instant) fades with a 5-hour half-life:
| Coffee at 3pm (100mg) | Caffeine left |
|---|---|
| 8pm | About 50mg |
| 1am | About 25mg |
| 6am | About 12mg |
Does more caffeine last longer? The half-life stays roughly the same, but a bigger dose leaves more behind. After 10 hours, 200mg leaves around 50mg in your system; 500mg leaves around 125mg, which is more than a whole cup of instant coffee. The same maths applies whatever the drink, so a matcha, a cola or an energy drink lasts as long as coffee does for the same amount of caffeine. See matcha benefits for how much is in a serving.
What makes caffeine last longer or shorter?
| Factor | Effect on caffeine | What studies found |
|---|---|---|
| Smoking | Clears faster | Average half-life 3.5 hours in smokers vs 6 hours in non-smokers |
| Combined contraceptive pill | Clears slower | About 10.7 hours vs 6.2 hours in women not on the pill |
| Pregnancy | Clears much slower | From about 3 hours to 10.5 hours in the last 4 weeks of pregnancy |
| Liver disease | Clears much slower | Cirrhosis has the biggest effect of any condition studied |
| Fluvoxamine (an antidepressant) | Clears far slower | Half-life rose from about 5 hours to 56 hours |
| Ciprofloxacin (an antibiotic) | Clears slower | Half-life rose from about 5 to 8 hours |
| Genetics (CYP1A2) | Either way | Some people are naturally fast or slow processors |
Men and women not on the pill clear caffeine at much the same rate. If you take any regular medicine, ask your pharmacist whether it affects caffeine, and don’t stop or change a medicine on your own. If caffeine makes you shaky or on edge, see does caffeine cause anxiety?
How much caffeine is in UK drinks?
| Drink or food | Approximate caffeine (NHS) |
|---|---|
| Cup of instant coffee | 100mg |
| Filter or coffee-shop coffee | Often more than 100mg |
| Energy drink (250ml can) | 80mg |
| Cup of tea (black or green) | 75mg |
| Can of cola | 40mg |
| 50g bar of plain dark chocolate | Under 25mg |
| 50g bar of milk chocolate | Under 10mg |
Large coffee-shop sizes and extra shots can add up fast. Drinking coffee before breakfast doesn’t change how long it lasts, but some people feel it more; see coffee on an empty stomach. For cans, see energy drinks, and for a lower-caffeine cup, mushroom coffee.
When to stop caffeine for sleep
In a home sleep study, 12 adults took 400mg of caffeine (about four cups of instant) at bedtime, 3 hours before or 6 hours before. All three timings disturbed sleep. Even at 6 hours, a sleep monitor showed more than an hour less sleep, while people’s own diaries suggested only around 40 minutes lost. You may not notice what late caffeine costs you.
The NHS advises no tea or coffee for at least 6 hours before bed if you struggle to sleep. “Stop by 2pm” is a handy rule of thumb that gives a 10 to 11pm sleeper 8 hours or more of clearance. Go earlier if you’re a slow processor, on the pill or pregnant.
| Your bedtime | Last caffeine (6 hours) | If you’re sensitive (8 hours) |
|---|---|---|
| 10pm | 4pm | 2pm |
| 11pm | 5pm | 3pm |
| Midnight | 6pm | 4pm |
Caffeine works by blocking adenosine, the chemical that builds sleepiness through the day. If you’re lying awake, start with sleep hygiene, a steady body clock and a bedtime routine. If poor sleep goes on for months, read our insomnia guide and speak to your GP.
Evening swaps
If you love a warm drink after dinner, choose something with little or no caffeine: chamomile tea or another herbal tea, or a mug of hot chocolate (see healthy hot chocolate).
Our Reishi Mushroom Adaptogenic Complex is a reishi hot chocolate made with reishi mushroom extract, organic cacao, maca, coconut milk powder and coconut sugar. Cacao contains a little natural caffeine, so it isn’t caffeine-free, but many people enjoy it as a cosy evening cup in place of coffee.
How much caffeine is safe?
- Healthy adults: EFSA considers up to 400mg a day, spread through the day, and single doses up to 200mg safe. Single doses of 100mg close to bedtime may affect sleep in some adults.
- Pregnancy: the NHS advises no more than 200mg a day.
- Breastfeeding: the NHS also advises no more than 200mg a day. Caffeine can reach your baby through breast milk and may make them restless, so it’s worth cutting down, especially while your baby is under 6 months.
- Children and teenagers: EFSA suggests no more than 3mg per kg of body weight a day, so about 120mg for a 40kg child.
A 500mg dose is well over the single-dose level EFSA considers safe.
Can you get caffeine out of your system faster?
Not really. Your liver clears caffeine at its own pace, and drinking lots of water, exercising, sweating it out or eating won’t meaningfully speed that up. What you can do:
- Stop having more caffeine, including tea, cola and chocolate.
- Go for a gentle walk or try slow breathing if you feel jittery; it won’t clear caffeine but may help you feel calmer while you wait.
- Next time, have smaller amounts earlier in the day.
- If your eyelid has started to flicker, caffeine is a common trigger; see eye twitching.
If you’ve had a lot of caffeine and get chest pain, a very fast or irregular heartbeat, or feel very unwell, get urgent medical help.
Caffeine withdrawal: how long it lasts
A major review of caffeine withdrawal found symptoms usually start 12 to 24 hours after your last dose, peak between about 20 and 51 hours, and last 2 to 9 days. Headache affected about half of people in experiments. Other common symptoms are tiredness, low energy, drowsiness, low mood, irritability and poor concentration. Stopping as little as 100mg a day was enough to cause symptoms in some people.
To cut down without the headache, reduce slowly over a week or two: swap one coffee for half-caff or tea, then move your last cup earlier. If you wake up with a headache at weekends, a later-than-usual first coffee may be why. For energy without extra caffeine, see how to boost energy naturally.
Related guides
- If you feel wired and anxious in bed, see why anxiety is worse at night.
- Want a lower-caffeine cup? See our coffee alternatives guide.
- Decaf coffee and sleep: how much caffeine it still has.
- Why you feel tired but too wired to sleep.
- See our full guide to caffeine withdrawal symptoms and timeline.
FAQs
How long does caffeine last?
You’ll usually feel it within 15 to 45 minutes, it peaks at around 30 to 60 minutes, and its half-life is about 3 to 6 hours. A quarter can still be in your system 10 or more hours later.
How long does caffeine stay in your system?
Most of it is gone within about 24 hours for healthy adults. It stays longer in pregnancy, on the combined pill, with liver disease and with some medicines.
Does caffeine last all day?
The noticeable buzz usually fades after a few hours, but caffeine is still in your body. A morning coffee is mostly cleared by bedtime; an afternoon one may not be.
How long does 200mg of caffeine last?
With a 5-hour half-life, about 100mg is left after 5 hours, 50mg after 10 hours and 25mg after 15 hours.
What time should I stop drinking caffeine?
At least 6 hours before bed, as the NHS advises. Stopping by about 2pm is a good rule of thumb if you go to bed around 10 to 11pm, or if you’re sensitive to caffeine.
How long does caffeine last in breast milk?
Caffeine can pass into breast milk and may make your baby restless. The NHS advises no more than 200mg a day while breastfeeding, and cutting down especially while your baby is under 6 months.
Sources
- Blanchard J, Sawers SJ (1983). The absolute bioavailability of caffeine in man. European Journal of Clinical Pharmacology.
- Liguori A et al (1997). Absorption and subjective effects of caffeine from coffee, cola and capsules. Pharmacology Biochemistry and Behavior.
- Mort JR, Kruse HR (2008). Timing of blood pressure measurement related to caffeine consumption. Annals of Pharmacotherapy.
- Nehlig A (2018). Interindividual differences in caffeine metabolism and factors driving caffeine consumption. Pharmacological Reviews.
- Grzegorzewski J et al (2022). Pharmacokinetics of caffeine: a systematic analysis of reported data. Frontiers in Pharmacology.
- Parsons WD, Neims AH (1978). Effect of smoking on caffeine clearance. Clinical Pharmacology and Therapeutics.
- Patwardhan RV et al (1980). Impaired elimination of caffeine by oral contraceptive steroids. Journal of Laboratory and Clinical Medicine.
- Knutti R et al (1982). The effect of pregnancy on the pharmacokinetics of caffeine. Archives of Toxicology.
- Culm-Merdek KE et al (2005). Fluvoxamine impairs single-dose caffeine clearance. British Journal of Clinical Pharmacology.
- Healy DP et al (1989). Interaction between oral ciprofloxacin and caffeine in normal volunteers. Antimicrobial Agents and Chemotherapy.
- Drake C et al (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine.
- Juliano LM, Griffiths RR (2004). A critical review of caffeine withdrawal. Psychopharmacology.
- EFSA. Caffeine.
- NHS. Foods to avoid in pregnancy (caffeine content of drinks).
- NHS. Breastfeeding and diet.
- NHS. Twitching eyes and muscles.
- NHS. Insomnia.
This guide is general information, not medical advice. Evopure makes the Reishi Mushroom Adaptogenic Complex.
