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Use caffeine to help you live on the new time zone, not to fight it. Take it only in the local morning and early afternoon at your destination, keep each serving at or below 200 mg, and stop early enough that it does not spoil your first nights there. Daylight and a fixed local bedtime do most of the work; caffeine only supports them.
Key takeaways
- Fix your destination bedtime first and plan caffeine backwards from it.
- Use caffeine only in the local morning and early afternoon.
- Keep each serving at or below 200 mg and the daily total at or below 400 mg.
- Light timing matters: morning light helps after flying east; avoid early-morning light after flying west.
- Do not mix caffeine with alcohol, including on the plane.
This page is education for healthy adults aged 18 and over. It is general information, not medical advice. If you take timed medication, ask your doctor how to adjust it across time zones.
Why caffeine helps with jet lag, and where it stops
Jet lag happens because your body clock is still on home time while the clock on the wall has moved. Caffeine blocks some of the signals that make you feel sleepy, so it can keep you alert through a local afternoon when your body thinks it is the middle of the night.
What it does not do is reset your body clock. Light and sleep timing do most of that work. The NHS page on jet lag advises going outside during the day because natural light helps your body clock adjust, switching to the new sleep times quickly, and not drinking too much caffeine or alcohol, which can make jet lag worse. It says jet lag usually improves within a few days.
The CDC Yellow Book chapter on jet lag, written for clinicians, suggests caffeine during daylight hours at your destination as needed for alertness, and stopping at least 6 hours before bedtime. Our advice below is a little stricter on timing, because a 2023 meta-analysis found that a normal coffee is best taken about 9 hours before bed to avoid losing sleep.
How fast your body clock catches up
The CDC chapter gives an average adjustment of about 1 hour a day after flying east and about 1.5 hours a day after flying west. So a five-hour time change can take several days to settle fully.
| Direction | What you need | Light | Caffeine |
|---|---|---|---|
| Flying east (for example London to Dubai or Asia) | Fall asleep earlier than your body wants | Get bright light in the early morning; avoid it in the evening | Morning only; be strict with the cut-off |
| Flying west (for example London to New York) | Stay up later than your body wants | Avoid bright light in the early morning; get afternoon light | Morning and early afternoon to hold on until local bedtime |
Step 1: Decide your destination bedtime before you travel
Pick the local time you want to go to bed on the first night and stick to it. Everything else, including caffeine, is planned backwards from that time. Treat it as fixed even if you feel wide awake or completely shattered.
Step 2: On the flight, keep caffeine light
- If it is night-time at your destination: skip caffeine and try to rest. Use an eye mask and earplugs.
- If it is daytime at your destination: a single coffee or tea is fine, but do not stack cups because the drinks trolley keeps coming round.
- Drink water regularly. Do not use alcohol to sleep on a flight, and do not mix caffeine with alcohol.
Step 3: Day one at your destination
- Morning: get outside in daylight (following the direction table above) and have your first caffeine with breakfast. A regular mug of coffee or a couple of cups of tea is enough for most people.
- Early afternoon: if you hit a wall, a second small serving is reasonable, ideally by early afternoon. The NHS suggests avoiding daytime naps; if you truly cannot stay awake, keep any nap very short and set an alarm.
- Late afternoon and evening: no caffeine. Use daylight, a walk, a shower and food to stay up until your planned bedtime.
Keep each serving at or below 200 mg and your daily total at or below 400 mg from all sources. The European Food Safety Authority (EFSA) says these amounts do not raise safety concerns for healthy adults. Airport and hotel coffees can be large, so count servings, not cups.
Step 4: Days two to four
Repeat the same pattern: caffeine in the local morning, perhaps one small top-up early in the afternoon, nothing later. Resist the urge to "catch up" with bigger doses after a bad night. Higher doses make the next night worse, and the cycle drags on.
If you are only away for one or two days, it can make more sense to stay roughly on home time rather than switching fully. Decide which plan you are following before you go.
Worked example: London to New York, midday arrival
Example: Maya flies from London to New York, a five-hour time change westward, landing around midday local time. She plans a 10pm local bedtime. The caffeine figures are rough estimates for illustration.
| Local New York time | What she does |
|---|---|
| On the flight (London morning) | One coffee with the first meal (estimated 80 to 100 mg), then water |
| 12pm (5pm in London) | Lands, goes outside, eats a light lunch |
| 1:30pm | One small coffee or tea if needed (estimated 75 to 100 mg); her last caffeine of the day |
| 2pm to 6pm | Walks in afternoon daylight; no nap |
| 10pm (3am in London) | Bed, with an alarm set for 7am |
| Next morning | Coffee with breakfast; avoids very bright light first thing; repeats the pattern |
Her total on day one is about 155 to 200 mg, and her last caffeine is more than 8 hours before bed. At the CDC's average of about 1.5 hours a day for westward travel, she can expect to feel mostly settled within three to four days. This is an illustration of the method, not a promised result.
Who should avoid caffeine or ask first
Some people should avoid or limit caffeine and check with their doctor or pharmacist first: anyone pregnant or breastfeeding (the NHS advises no more than 200 mg a day in pregnancy), anyone under 18, people with heart conditions or high blood pressure, people with anxiety or panic disorders, and anyone taking medicines that may interact with caffeine. Never use caffeine powders or highly concentrated liquid caffeine.
FAQ
Should I drink coffee on a long-haul flight?
Only if it is daytime at your destination. If it is night there, skip it and try to sleep, so you land closer to the local rhythm.
What time should I stop caffeine on the first day?
Base it on your local bedtime, not home time. The CDC suggests at least 6 hours before bed; for a normal coffee, a cut-off around 9 hours before bed is gentler on sleep.
Can I use energy drinks to get through jet lag?
They work like coffee, but large cans can contain a lot of caffeine and sugar. If you use one, read the label and count it in your daily total.
How long does jet lag last?
The NHS says it usually improves within a few days. The CDC gives an average body-clock shift of about 1 hour a day after flying east and 1.5 hours a day after flying west.
Does melatonin help with jet lag?
The NHS says melatonin tablets are not recommended on the NHS for jet lag because there is not enough evidence they work. Ask a doctor before taking any sleep aid.
If you want a full system for timing caffeine around travel, work and sleep, our book Secrets to Using Caffeine to Win lays it out for healthy adults within the 400 mg and 200 mg limits.
Related guides: how shift workers should time caffeine on night shifts, does caffeine ruin deep sleep even if you can still fall asleep? and should you wait 90 minutes after waking before coffee?
This is general information, not medical advice.