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For adult students, a good exam-period plan is simple: keep your usual moderate amount rather than ramping up, drink it in the morning before your hardest revision, stop early enough to protect sleep, and on exam day have a familiar, moderate dose rather than anything new or large. Sleep does more for memory and exam performance than extra caffeine, so the plan is built around protecting it.
Check your daily total and your cut-off with the free Caffeine Cutoff Calculator, and see a sample study day in the free 2-page preview.
This page is education for healthy adults aged 18 and over, such as university students. It is general information, not medical advice. If you are under 18, this plan is not for you; talk to a parent, school nurse or GP instead.
The limits to plan around
The European Food Safety Authority (EFSA) says that for healthy adults, daily intakes up to 400 mg from all sources and single doses up to 200 mg do not raise safety concerns. Count everything: coffee, tea, cola, energy drinks and caffeine tablets.
As a rough guide, the NHS gives about 100 mg for a mug of instant coffee, about 75 mg for a mug of tea, about 40 mg for a can of cola and about 80 mg for a 250 ml energy drink. Larger cans and coffee-shop drinks can contain much more, so read labels.
Step 1: Don't ramp up during revision
Exam season tempts people to double their usual intake. That tends to backfire: higher doses bring jitters, a racing mind and worse sleep, and stopping suddenly afterwards can bring headaches and tiredness. Aim to stay at, or a little below, what you normally drink.
Step 2: Time caffeine to your hardest revision
- Plan your day so the most demanding work (past papers, problem sets, new material) comes first.
- Have your first coffee or tea as you start that block, not when you first wake up and scroll.
- If you need a second serving, have it late morning or around lunchtime.
- Use easier tasks, such as flashcards or tidying notes, for the later part of the day.
Step 3: Protect sleep with a cut-off
A 2023 meta-analysis in Sleep Medicine Reviews (Gardiner and colleagues) found caffeine reduced total sleep and deep sleep on average, and suggested finishing a typical coffee at least about 9 hours before bed. If you sleep at midnight, that means stopping regular coffee around 3pm. Avoid all-nighters: losing sleep before an exam usually costs more than the extra hours of revision gain.
Step 4: The exam-day routine
- Have your normal amount, not more. Exam day is not the day to try a big energy drink, caffeine tablets or a new pre-workout. A familiar dose means familiar effects.
- Time it before the exam. Have your usual coffee or tea with breakfast or in the hour before a morning exam. For an afternoon exam, have it with lunch, keeping your cut-off in mind.
- Eat properly. A balanced breakfast or lunch helps you avoid feeling shaky.
- Mind the toilet. Caffeine can make you need the toilet more, so time your drink and visit before you go in.
- Bring water, if allowed, rather than a second coffee.
Step 5: After the exams
Come down gently. If you've drunk more than usual during revision, cut back over a week or so rather than stopping overnight, which can ease withdrawal headaches and tiredness.
Who should avoid caffeine or ask first
Some people should avoid or limit caffeine and check with a GP or pharmacist first: anyone pregnant or breastfeeding (the NHS advises no more than 200 mg a day in pregnancy), children and teenagers under 18, people with heart conditions or high blood pressure, people with anxiety or panic disorders (exam stress can make this worse), people with sleep disorders, and anyone taking medicines that may interact with caffeine, including some prescribed for ADHD.
Never use caffeine powders or highly concentrated liquid caffeine, and never mix caffeine with alcohol, including at post-exam celebrations. The CDC explains that mixing alcohol and caffeine can make you feel less drunk than you are.
A worked example
Sam, 20, has a 9:30am exam and usually drinks two coffees a day. He goes to bed at 11pm the night before with no caffeine after 2pm, has his usual coffee with breakfast at 8am, drinks water during the exam, and has his second coffee at lunch. This shows how the plan works; it is not a promised result, and people respond differently.
Key takeaways
- Keep your usual moderate amount; don't ramp up for exams.
- Stay within 400 mg a day and 200 mg at once, counting every source.
- Use caffeine for your hardest morning revision, not late at night.
- Set a cut-off about 9 hours before bed and avoid all-nighters.
- On exam day, stick to a familiar dose and try nothing new.
FAQ
Should I drink an energy drink before an exam?
It is not recommended if you don't normally drink them. Large cans can contain a lot of caffeine and sugar. If you do, read the label, count it in your total and keep it under 200 mg.
Are caffeine tablets OK for revision?
Tablets make it easy to take large, fast doses. If you consider them, check the dose per tablet, never exceed 200 mg at once, and ask a pharmacist first, especially if you take any medicines.
I don't normally drink caffeine. Should I start for exams?
Probably not. Starting during exams means unfamiliar effects, possible jitters and worse sleep at the worst time. Focus on sleep, breaks and a good revision plan instead.
How long before an exam should I have coffee?
Many people have it with breakfast or about 30 to 60 minutes before they need to focus, but the more important thing is keeping to your usual dose and protecting the previous night's sleep.
If you want a full plan for timing caffeine around study and sleep, our book Secrets to Using Caffeine to Win (formerly Caffeine Leverage) covers it for healthy adults inside the 400 mg and 200 mg limits; it costs £82.80 one-time as an instant PDF: Secrets to Using Caffeine to Win. You can read the free 2-page preview first.
This is general information, not medical advice.
Last updated: 28 October 2026
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