How much caffeine is too much? Daily and single-dose limits

Key takeaways

• Healthy adults: up to 400 mg a day (FDA, EFSA, Health Canada), and up to 200 mg at one time (EFSA).
• Pregnancy: no more than 200 mg a day per the NHS and EFSA; Health Canada sets 300 mg, so ask your clinician and lean to the lower figure.
• Children and teens: weight-based guidance (2.5–3 mg per kg a day), and pediatricians say the caffeine and other stimulants in energy drinks have no place in their diet.
• Count milligrams, not cups: a 12-oz brewed coffee ranges from 113 to 247 mg in FDA figures.
• Breathing trouble, confusion, seizures or an irregular heartbeat after caffeine are an emergency.

Caffeine limits by group: adults, pregnancy, children and teens

The main health agencies agree closely for healthy adults. The FDA cites 400 mg a day as an amount not generally associated with negative effects for most adults. EFSA concluded that up to 400 mg a day spread across the day, and single doses up to 200 mg (about 3 mg per kg of body weight), raise no safety concerns for healthy adults, except pregnant women. Health Canada recommends no more than 400 mg a day for adults.

Pregnancy is where agencies differ. The NHS says not to have more than 200 mg a day, because too much caffeine has been linked to a higher chance of miscarriage and stillbirth. EFSA says up to 200 mg a day raises no safety concerns for the fetus, and MedlinePlus advises less than 200 mg. Health Canada sets 300 mg for people who are pregnant, breastfeeding or planning a pregnancy. When agencies differ, the lower figure plus a conversation with your midwife or doctor is the safe default.

For children and teens, guidance is based on body weight, and parents should discuss it with a health professional rather than work out a target.

How many cups of coffee a day is too much caffeine?

The FDA translates 400 mg into about two to three 12-oz cups of coffee, but cups are a shaky unit. In the FDA’s own figures, a 12-oz regular brewed coffee has 113 to 247 mg, and energy drinks generally have 54 to 328 mg per 16 oz. Lab tests of US coffee-shop coffees found 58 to 259 mg per serving, and the same drink from the same shop ranged from 259 to 564 mg over six days. One large shop coffee can therefore use up half or more of a day’s 400 mg.

The NHS gives rough figures for other drinks: about 100 mg in a mug of instant coffee, 75 mg in a cup of tea, 40 mg in a can of cola and 80 mg in a 250-ml energy drink. Caffeine from tea, chocolate and added caffeine all counts: the FDA says your body handles naturally occurring and added caffeine the same way.

To see what your day adds up to, check our caffeine chart or the brewed coffee page, and use the caffeine timing calculator to see how much is still in your system at bedtime. For a single drink, our guide to whether 200 mg is a lot puts doses into everyday terms.

Why your personal caffeine limit may be lower than 400 mg

The 400 mg figure is a population reference, not a personal target. The FDA says “too much” varies with body weight, medicines, medical conditions and individual sensitivity, and that people vary widely in how sensitive they are to caffeine and how fast they clear it. EFSA’s assessment did not cover people with medical conditions or caffeine taken together with medicines.

Sleep is affected well below the safety limits. EFSA says a single 100 mg dose may affect sleep in some adults, especially close to bedtime, and in a 2025 trial 400 mg taken within 12 hours of bed delayed sleep and changed its structure. Anxiety follows dose too: in 102 light caffeine users, 450 mg raised anxiety in most of them, while 50 mg did not.

MedlinePlus advises checking with your health care provider about limiting caffeine if you are pregnant or breastfeeding, have sleep problems, migraines, anxiety, reflux or ulcers, a heart rhythm problem or high blood pressure, or take certain medicines, including stimulants, some antibiotics, asthma and heart medicines. For medicine questions, ask your doctor or pharmacist.

Signs you’ve had too much caffeine in a day

The FDA lists these signs of too much caffeine, and advises talking with a health professional about your caffeine intake if you have any of them:

MedlinePlus adds restlessness, shakiness, dizziness and dependency. If you’re jittery right now, our guide on how to stop caffeine jitters covers what to do in the next hour, and our racing heart guide explains when a fast heartbeat needs checking.

• Faster heart rate or heart palpitations
• High blood pressure
• Insomnia or disrupted sleep
• Anxiety and jitters
• Upset stomach or nausea
• Headache

Caffeine overdose symptoms that need emergency help

MedlinePlus lists symptoms of caffeine overdose in adults including breathing trouble, confusion, agitation or hallucinations, seizures, an irregular or rapid heartbeat, vomiting, fever and muscle twitching. Its advice is to seek medical help right away. Call your local emergency number; in the US you can also reach Poison Help on 1-800-222-1222.

MedlinePlus also notes that caffeine overdose and an acute anxiety reaction can look very similar, so don’t try to decide which one it is on your own. The NHS says palpitations that come with chest pain, shortness of breath, or feeling faint or fainting need emergency care.

Why pure caffeine powder and liquid concentrates are so risky

Pure and highly concentrated caffeine products are in a different league from drinks. The FDA says one teaspoon of pure powdered caffeine can contain as much caffeine as 28 cups of coffee, and half a cup of a liquid concentrate more than 20 cups. The FDA warns that kitchen spoons can’t reliably measure a safe serving of these products, and it links them to at least two deaths in the US.

The FDA estimates that toxic effects such as seizures can occur with rapid intake of around 1,200 mg, which is less than half a teaspoon of pure caffeine. Don’t use pure caffeine powders or liquid concentrates, and keep any you find away from children.

Common questions