How Long Does Caffeine Last? Half-Life, Sleep and When to Stop (UK)

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:

The buzz often fades before the caffeine does, so you can feel flat mid-afternoon and still struggle to drop off at night.

Can caffeine make you tired?

Yes, coffee can leave you more tired, even though caffeine is a stimulant. It doesn’t remove tiredness; it hides it for a few hours. As caffeine wears off, the tiredness returns, and late cups, sugary drinks and daily withdrawal can make it worse. The usual reasons (checked October 2026):

• The crash. Adenosine builds sleep pressure while you’re awake. Caffeine blocks its receptors but can’t replace sleep, so tiredness returns as it fades. More in coffee crash and afternoon slump.
• Late caffeine. In the sleep study below, 400mg taken 6 hours before bed cost over an hour of sleep, leaving you more tired the next day (see tired but wired).
• Dehydration, rarely. The NHS counts tea and coffee towards your 6 to 8 daily cups of fluid.
• Sugar. The NHS sets a 30g daily limit on free sugars for adults, and a syrupy coffee with a pastry leaves some people sluggish (see tired after eating).
• Tolerance and withdrawal. In a Bristol study of 379 adults, regular drinkers given a dummy pill after 16 hours without caffeine felt less alert, and caffeine only returned them to normal. Tiredness is a core caffeine withdrawal symptom.

iIf you’ve been tired for a few weeks without knowing why, it affects daily life, or it comes with weight loss or mood changes, the NHS advises seeing a GP (see why you’re always tired).

Lower-caffeine evening swaps: which Evopure product fits your routine?

Start with the afternoon and evening cup: chamomile tea is caffeine-free and hot chocolate has only a little. Our options (checked October 2026):

Product	Format	When it fits	Caffeine
Magnesium Glycinate Sleep Complex	Berry drink powder, 290mg magnesium a serving	Evening, in place of a late tea or coffee	None
Reishi Mushroom Adaptogenic Complex	Reishi hot chocolate, 2 teaspoons (8g)	A warm cup after dinner	A little, from cacao
Flow CBD Oil with Ashwagandha and Maca	Oil, 500mg or 1,000mg	A morning routine while you cut back on coffee	None

Magnesium contributes to a reduction of tiredness and fatigue, so the caffeine-free Sleep Complex is the natural pick if tiredness is your worry.

Our reishi cacao contains a little natural caffeine: unsweetened cocoa has about 230mg per 100g, so a serving has far less than a 100mg instant coffee.

iFlow has no caffeine, and we make no energy claims. About 0.2ml (500mg) or 0.1ml (1,000mg) gives 10mg of CBD. It contains ashwagandha: avoid it with a thyroid, liver or autoimmune condition or before surgery, and ask your GP or pharmacist first if you take medication.

The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.

Value: the 1,000mg Flow costs less per mg than the 500mg. Subscribe and Save lowers every order’s price; skip, pause or cancel any time.

• Our CBD products: every batch third-party tested at ISO 17025 labs; request a batch report on our lab testing page.
• Flow is broad spectrum and THC free, and on the FSA public list, linked to validated applications.
• Made in the UK, vegan and alcohol-free.
• Tracked Royal Mail delivery, same-day dispatch before 3pm Monday to Thursday (delivery); unopened items returnable within 14 days (returns).

They’re food supplements, not medicines. We don’t recommend our products during pregnancy or breastfeeding. Adults 18+ only. Try the Sleep Complex in the evening, the reishi cacao after dinner or Flow in your morning routine.

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:

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?

iMen 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?

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.

iIf 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.

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, the same figure EFSA gives.
• 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. For energy without extra caffeine, see how to boost energy naturally.

Related guides

• Coffee alternatives and how much caffeine decaf still has.
• Caffeine withdrawal symptoms and timeline.
• Shaky hands from caffeine and waking up to pee at night.
• Caffeine in green tea and dark chocolate.
• CBD for studying, and CBD and caffeine (at very high doses CBD can slow how fast caffeine is cleared).
• A power nap of 10 to 20 minutes instead of a late coffee, and late-night sport and sleep.
• Caffeine in Four Sigmatic mushroom coffee, Pukka Night Time tea and Yogi Bedtime tea.
• Taking ashwagandha with coffee.
• Swapping your evening cuppa for a herbal one? Our best tea for sleep guide ranks the caffeine-free options by evidence.
• Cacao drinks contain a little caffeine too, which is why we suggest reishi cacao in the afternoon or early evening; see when to take reishi.
• Cutting caffeine earlier is the first step; if you are also weighing up a supplement, see which magnesium helps you sleep.
• Hot chocolate has some too, though far less than tea: see does hot chocolate have caffeine.
• If you’ve switched from smoking to vaping, caffeine lasts longer than it did, because tobacco smoke sped up how fast you cleared it (see does vaping make you tired).