Caffeine Overdose

How much caffeine is too much?

Doctors also call this caffeine intoxication when symptoms follow a recent high intake. Caffeine is a stimulant that blocks adenosine, a brain chemical that promotes sleepiness. In large doses it overstimulates the brain and heart, raises adrenaline levels and lowers blood potassium.

General guidance:

• Healthy adults: up to about 400 mg a day is not usually linked to harm.
• Pregnancy and breastfeeding: no more than 200 mg a day.
• Teenagers: the American Academy of Pediatrics advises against energy drinks for children and teens.
• Children: small bodies are much more sensitive. Caffeine pills can be dangerous for a toddler.

People vary greatly. Sensitivity is higher in people with anxiety, heart rhythm problems, high blood pressure and in those taking certain medicines that slow caffeine clearance, such as the antibiotic ciprofloxacin and the antidepressant fluvoxamine. Pregnancy and liver disease also slow clearance.

Typical caffeine content

The FDA has warned that a single teaspoon of pure powdered caffeine can contain as much as about 28 cups of coffee, which is potentially lethal. Bulk pure and highly concentrated caffeine products have been the cause of several deaths.

Symptoms of a caffeine overdose

Mild to moderate

• jitteriness, shaking hands (tremor)
• restlessness, anxiety and irritability
• fast heartbeat and palpitations
• nausea, stomach upset and diarrhea
• headache and dizziness
• frequent urination
• flushing and sweating
• difficulty sleeping

Severe

• repeated vomiting
• chest pain
• very fast or irregular heart rhythms, including atrial fibrillation and dangerous ventricular rhythms
• low blood pressure after an initial rise
• fast breathing
• confusion, agitation, hallucinations
• muscle twitching and muscle breakdown (rhabdomyolysis)
• seizures
• very low potassium, which can trigger arrhythmias

Severe toxicity in adults usually involves several grams of caffeine taken at once. Serious harm can occur at much lower doses in children and in people with heart conditions.

Caffeine overdose vs panic attack

The symptoms overlap: racing heart, trembling, sweating, a sense of dread. A panic attack usually peaks within 10 minutes and passes within about half an hour, while caffeine effects last for hours. Caffeine can also trigger panic attacks in people prone to them.

What to do if you have too much caffeine

For mild symptoms after coffee, tea, soda or a single energy drink:

1. Stop taking any more caffeine.
2. Drink water to stay hydrated.
3. Take a short, gentle walk, or sit somewhere calm.
4. Practice slow breathing to ease anxiety.
5. Eat a light snack if you feel shaky or nauseated.
6. Wait. Caffeine levels fall by half about every 3 to 6 hours in healthy adults.

There is no home remedy that removes caffeine faster. Do not take other stimulants or alcohol to counteract it.

Call Poison Control (1-800-222-1222 in the US) for advice after swallowing caffeine pills or concentrated caffeine, or if a child has swallowed caffeine. Call 911 for any emergency symptoms listed above.

Hospital treatment

• heart monitoring and blood tests for potassium, glucose, kidney function and muscle enzymes
• activated charcoal if the person arrives early after a large ingestion and can protect their airway
• intravenous fluids and potassium replacement
• benzodiazepines for agitation and seizures
• medicines to control heart rhythm and blood pressure
• hemodialysis for life-threatening overdoses, which removes caffeine from the blood

Most people treated promptly recover fully within a day or two.

Prevention

• Track your daily caffeine from all sources, including pre-workout supplements, energy shots, chocolate and some pain relievers.
• Avoid pure powdered or concentrated liquid caffeine products.
• Keep caffeine tablets and energy shots out of reach of children.
• Do not mix energy drinks with alcohol, which masks intoxication.
• Cut down gradually if you drink a lot, to avoid withdrawal headaches.

Frequently asked questions

How much caffeine causes an overdose?

Symptoms of too much caffeine often appear above about 400 mg in a sitting for sensitive people, and severe toxicity typically needs several grams taken at once in adults. A teaspoon of pure powdered caffeine can be lethal. Children and people with heart conditions are affected at much lower doses.

What are the first signs of too much caffeine?

Early signs are jitteriness, shaky hands, restlessness, anxiety, a fast or pounding heartbeat, upset stomach and needing to urinate often. Chest pain, an irregular heartbeat, repeated vomiting, confusion or seizures are signs of serious toxicity and need emergency care.

How long does a caffeine overdose last?

Mild symptoms usually ease within 4 to 6 hours, though trouble sleeping may last into the night. Caffeine's half-life in adults is about 3 to 6 hours, longer in pregnancy, liver disease and with some medicines. Severe overdoses can cause effects for a day or more and need hospital care.

Can you die from a caffeine overdose?

Yes, but it is rare and almost always involves caffeine pills or pure powdered or liquid caffeine rather than coffee. Deaths are usually from dangerous heart rhythms or seizures. It is very difficult to reach a lethal dose from brewed coffee alone.