Caffeine, energy drinks and smart napping

Caffeine is the world's favourite energy fix, and naps are the oldest one. Both can help or quietly wreck your sleep, depending on how much, how late and how long.

Watch the 1-minute overview

Watch the full video guide for this module

How caffeine works on your sleep

• Yale Medicine notes that caffeine typically starts working within 30 to 45 minutes and has a half-life of about five to six hours, meaning half of it is still active that long after you drink it.
• The NHS says the effects of caffeine on the body can last up to 7 hours.
• Worked example: a large iced coffee at 5pm could still have about half its caffeine active at 10pm or 11pm, right when your body clock is trying to wind down.
• UCLA Health advises teens to avoid caffeine, including soda and chocolate, after 4pm; a sleep doctor quoted by Yale Medicine suggests no caffeine after 1pm or 2pm. Earlier is safer.

How much is too much for a teenager

• The FDA's 400 milligrams a day figure is for most healthy adults, not teenagers (FDA, Yale Medicine).
• Yale Medicine (2026) reports that the American Academy of Pediatrics (AAP) recommends adolescents avoid energy drinks entirely and cap caffeine at 100 milligrams a day.
• The European Food Safety Authority (EFSA) proposes a safety level of 3mg per kg of body weight per day for habitual caffeine intake by children and adolescents. For a 50kg teenager that works out at 150mg.
• These guides come from different bodies (a US paediatric body and a European food safety authority) and give different figures. The cautious choice is the lower one: stay at or below about 100mg a day, with none in the afternoon or evening. This is a general guide, not a personal recommendation.
• EFSA notes that, in adults, single doses of 100mg may affect sleep duration and patterns, particularly when taken close to bedtime.

Where caffeine hides

• The FDA gives these ranges per 12 fluid ounces (about 355ml): caffeinated soft drinks 23 to 83mg, green tea 37mg, black tea 71mg, regular brewed coffee 113 to 247mg, energy drinks 41 to 246mg.
• The FDA adds that energy drinks generally contain 54 to 328mg per 16 fluid ounces (about 473ml). A single large can can therefore exceed a teen's whole-day limit.
• Specialty coffees, cold brew and large café sizes can be much higher than a home-made cup. Check the label or the café's website.
• Yale Medicine also lists chocolate, chewing gum, caffeinated sodas and caffeine pouches (typically 50 to 200mg each) as hidden sources.
• The FDA warns that pure and highly concentrated caffeine products can have serious health consequences, including death. Never use caffeine powders or tablets.

Energy drinks

• The FDA states that medical experts advise against energy drinks for children and teens because of their sugar and caffeine levels.
• A paediatric specialist at Burjeel Medical City in Abu Dhabi has said it is generally not recommended for under-18s to consume energy drinks.
• Signs of too much caffeine listed by the FDA include a racing heart, palpitations, sleep disruption, anxiety, jitters, an upset stomach, nausea and headache.
• If you rely on caffeine daily, cut down gradually rather than stopping suddenly. The FDA notes that withdrawal is not dangerous but can be unpleasant, and the NHS says stopping suddenly can lead to insomnia and headaches.
• If you notice these signs, stop and talk to a doctor or pharmacist. If you have chest pain or feel very unwell, get urgent help; in the UAE call 998 for an ambulance in an emergency.

Napping the smart way

• The Sleep Foundation says the best nap length for adults is about 20 minutes and no longer than 30 minutes, because waking from deep sleep can leave you groggy.
• Timing matters: the Sleep Foundation says experts typically recommend adults nap eight or more hours before bedtime, which for most people means before about 3pm.
• UCLA Health suggests teens who must nap keep it under an hour.
• Naps are a top-up, not a replacement. If you regularly need a nap to function, look at your night-time sleep first.
• If you have trouble sleeping at night, the NHS lists avoiding daytime naps among its tips for sleeping well, because naps can reduce your sleep drive at bedtime.