Caffeine Intoxication

How much caffeine is too much?

Caffeine is a stimulant that blocks adenosine, a brain chemical that promotes sleepiness. It also releases adrenaline, raising heart rate and blood pressure. Sensitivity varies widely with genetics, body size, tolerance, medicines and liver function.

Typical caffeine content (amounts vary by brand):

The FDA has warned that pure and highly concentrated caffeine powders and liquids are dangerous because a toxic dose can be accidentally measured in a single spoonful.

Symptoms

Caffeine intoxication is diagnosed when recent heavy caffeine use causes several of these symptoms:

• restlessness, nervousness and excitement
• anxiety or a sense of panic
• insomnia
• flushed face
• frequent urination
• stomach upset, nausea or diarrhea
• muscle twitching and shaky hands
• rambling thoughts or speech
• fast or irregular heartbeat (palpitations)
• periods of inexhaustibility
• agitation

Severe caffeine toxicity

Very high doses, usually from pills, powders or supplements, can cause:

• vomiting that will not stop
• dangerous heart rhythms such as ventricular tachycardia
• low potassium (hypokalemia)
• high blood sugar and acid build-up
• seizures
• muscle breakdown (rhabdomyolysis)
• death, rarely, typically with intakes of several grams

Serious toxicity is more likely at doses above about 1,200 mg taken quickly. Fatal cases usually involve 10 g or more, but lower doses can be dangerous in people with heart conditions. See also caffeine overdose for the emergency picture.

Who is at higher risk

• people with heart rhythm problems, high blood pressure or anxiety disorders
• pregnant women
• children and teens
• people taking medicines that slow caffeine breakdown, such as fluvoxamine, ciprofloxacin and some oral contraceptives
• people with liver disease
• people using stimulant medicines, decongestants or other stimulants together with caffeine
• people who are not regular caffeine users

Diagnosis

A doctor will ask what was consumed, how much and when, and about medicines and supplements. They will check heart rate, blood pressure and heart rhythm (ECG). In severe cases, blood tests check potassium, glucose, acid levels and muscle enzymes. Caffeine blood levels can be measured but are not usually needed for mild cases.

Treatment

Mild intoxication at home

• Stop all caffeine immediately.
• Drink water, in moderate amounts.
• Eat a light meal or snack to slow absorption and ease nausea.
• Walk gently or practice slow breathing to ease jitters.
• Wait it out: caffeine's half-life is about 3 to 6 hours in healthy adults, longer in pregnancy and liver disease.
• Avoid other stimulants, decongestants and alcohol.

There is no antidote, and "sleeping it off" or exercising hard does not speed elimination.

Hospital treatment for severe cases

• activated charcoal if the person arrives soon after swallowing pills or powder
• IV fluids and replacement of potassium
• medicines to control vomiting, agitation and seizures
• treatment of heart rhythm problems
• dialysis in life-threatening cases

Prevention

• Know the caffeine content of what you drink and add it up across the day.
• Avoid pure or concentrated caffeine powders and liquids.
• Read labels on pre-workout and weight-loss supplements.
• Avoid mixing energy drinks with alcohol, which masks intoxication.
• Keep caffeine pills away from children.
• Cut back gradually if you rely on caffeine, to avoid withdrawal headaches and fatigue.

Frequently asked questions

What are the symptoms of too much caffeine?

Common symptoms are restlessness, nervousness, a racing or pounding heart, shaky hands, nausea, upset stomach, frequent urination, headache and trouble sleeping. Severe toxicity can cause vomiting, an irregular heartbeat, confusion and seizures, which need emergency care.

How much caffeine is too much in a day?

For most healthy adults, up to about 400 mg a day is considered safe, roughly 4 cups of brewed coffee. Pregnant women should stay under 200 mg. Intoxication symptoms often appear after more than about 250 mg in a short time, depending on sensitivity.

What should I do if I drank too much caffeine?

Stop caffeine, drink some water, eat something light and rest. Symptoms usually ease within 4 to 6 hours. Seek emergency care for chest pain, fainting, seizures, confusion or a very fast or irregular heartbeat, and call Poison Control after any large dose of pills or powder.

How long does caffeine intoxication last?

Mild symptoms usually fade within 4 to 6 hours as caffeine is cleared, though sleep may be affected for longer. Caffeine lasts longer in pregnancy, with liver disease or when taking certain medicines. Severe toxicity can need hospital treatment for a day or more.

Can too much caffeine kill you?

Yes, but it is rare and usually involves very large doses from pills, powders or concentrated products, often several grams. Coffee and tea alone rarely cause fatal toxicity because large volumes would be needed. People with heart problems are more vulnerable.