What Are the Signs of Caffeine Overdose?

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Caffeine is a stimulant that triggers the central nervous system. It is the most widely consumed psychoactive substance in the world. In moderate doses, caffeine makes us feel good. But in amounts above 400 milligrams per day, caffeine overdose is possible.

This article reviews caffeine consumption guidelines, high-caffeine drinks, and what to do if you've had too much caffeine

Girl with headphones drinking caffeine

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Recommended Dosage of Caffeine

Consuming less than 400 milligrams (mg) of caffeine per day is considered a safe dosage for most healthy adults without any medical conditions. The U.S. Food and Drug Administration (FDA) considers excessive caffeine consumption anything above 400 mg/day.

Children under age 12 should avoid caffeine. Teenagers should limit their caffeine intake to about 100 mg per day. Kids and teens should also avoid consuming energy drinks.

Caffeine and Pregnancy

Before 2021, moderate caffeine consumption (less than 200 mg) during pregnancy was generally considered safe. However, emerging evidence suggests much lower daily dosages (50 mg/day) may result in smaller birth sizes.

Sources of Caffeine

Over 60 plants contain caffeine. The most common natural caffeine sources are:

  • Coffee beans
  • Tea leaves
  • Kola nuts (used in colas)
  • Cacao pods (used in chocolate)

Some caffeine is made artificially and added to soft drinks or other products.

A breakdown of caffeine measurements per source is provided below.

Source of Caffeine Milligrams (mg) per serving
Coffee 60-95 mg/8 ounces
Espresso 65 mg/1.5 ounces
Black Tea 47 mg/8 ounces
Soda (cola) 40-55 mg/12 ounces
Energy drinks 85-200 mg/8 ounces
Chocolate (cacao) 24 mg/1 ounce
Caffeine tablets 200 mg/per pill

Risks and Benefits of Caffeine

Caffeine increases awareness, reduces fatigue, and lifts mood. It can also improve physical and cognitive performance. Low to moderate doses (40 mg to 300 mg) can improve the following:

In moderate to high doses (200 mg to 400 mg), caffeine can improve athletic performance. Athletes who consume very little caffeine (< 40 mg/day) on a regular basis feel the effects more on game day.

Sports-related benefits of caffeine include:

  • Endurance and stamina
  • Hand-eye coordination
  • Peripheral awareness
  • Faster sprints

Caffeine consumption comes with risks. Too much caffeine instantly undoes all of its benefits. Although drinking too much coffee or tea can be risky, energy drinks and highly concentrated caffeine in dietary supplements (pills, powders, liquid shots) present the biggest overdose risk.

One teaspoon of pure powdered caffeine can equal 28 cups of coffee. The recommended dose of 1/16 teaspoon is tiny and difficult to measure accurately. Accidental measurement errors are common. A simple mistake of using 1/4 teaspoon could result in a toxic dose being consumed.

Caffeine can be lethal, but fatalities from caffeine are extremely rare. A lethal dose of caffeine is about 5 to 10 grams (5,000 to 10,000 mg) or 150 to 200 mg per kilogram of body weight.

Sub-lethal caffeine overdose may cause symptoms such as chills, flushing, headache, nausea, heart palpitations, and tremors. Excessive consumption of products containing caffeine can also cause rhabdomyolysis and acute kidney injury.

When someone dies from a caffeine overdose, the cause of death is often described as ventricular fibrillation (erratic heartbeat).

Calculating Caffeine Intake

If you're curious how much caffeine is appropriate for you and your body type, this caffeine calculator identifies how much caffeine is dangerous based on body weight in pounds or kilos.

Side Effects of Too Much Caffeine

Signs of too much caffeine include anxiety, feeling jittery, insomnia, GI issues, and having your heart race over 100 beats per minute (tachycardia). In rare cases, caffeine toxicity results in death. Individual responses to any dose of caffeine can vary significantly.

Caffeine overdose can cause the following symptoms:

Caffeine Sensitivity

Not everyone responds to caffeine the same way. Recommended dosages should be viewed as loose guidelines. Caffeine allergy can cause overdose symptoms at doses below 100 mg. Genetic differences linked to the ADORA2A gene make some people hypersensitive to caffeine.


Exactly how much caffeine is dangerous varies from person to person. If you or someone else accidentally consumes too much caffeine and has overdose symptoms, contact Poison Control right away. Call 911 in the case of emergencies.

Poison Control Contact Information

If you or someone you know has overdosed on caffeine, help is available 24/7 online at the Poison Control website or by phone at 1-800-222-1222. Both options are free and confidential.

Preventing Caffeine Overdose

Educating yourself about how much caffeine is in everything you eat, drink, or swallow is the best way to prevent caffeine overdose.

Caffeine is often hidden in products. Read labels closely and keep tabs on how many milligrams of caffeine you consume each day.

Certain medications increase the risk of caffeine toxicity, including:

Accidental caffeine overdose can occur if these are taken with daily amounts of coffee, tea, or soda.

Speak with a healthcare provider about how much caffeine is in the medication you take. Cut back on typical daily intake of caffeine-containing products while taking these medicines to avoid caffeine overdose.

Read Instructions Carefully

Highly-concentrated forms of caffeine are most likely to cause an accidental overdose. Always use extreme caution when taking any concentrated form of caffeine and follow measurement instructions very closely.


Overdosing on caffeine is rare, but accidental overdoses happen. The recommended amount of caffeine that adults can consume for their health and safety is approximately 400 milligrams (mg) per day. Children under 12 should avoid caffeine. Teens should limit caffeine to about 100 mg per day.

Energy drinks are one of the most common ways to accidentally overdose on caffeine. Read energy drink labels closely and calculate how much caffeine is in each container. Serving sizes and caffeine per fluid ounce can vary greatly. Call Poison Control or 911 immediately in caffeine-related emergencies.

A Word From Verywell

People of all ages are at risk of caffeine overdose. If you want to cut back on caffeine to lower your risk, there are healthy alternatives. Eating a nutritious diet and getting enough sleep will give you the energy to power through the day with less caffeine. Anytime you cut back on your daily caffeine intake, do so gradually. Caffeine withdrawal is avoidable if you don't go cold turkey. 

Frequently Asked Questions

  • How common is caffeine overdose?

    Caffeine overdose happens, but it's not common. Although caffeine-related deaths are extremely rare, emergency room visits due to energy drinks are a public health concern. From 2007 to 2011, ER visits related to caffeine overdose from energy drinks doubled from 10,068 to 20,783 visits. 

  • What alternatives to coffee can help you wake up in the morning?

    Yerba mate, brewed cacao (for chocolate lovers), matcha, and brewed chicory are vitalizing alternatives with less caffeine than coffee beans. These drinks can perk you up with much less caffeine than you'd find in a cup of coffee.

  • Can certain foods give you an instant energy boost?

    A few bites of chocolate can give you instant energy. Nibbling on goji berries also makes people feel energetic. Bananas provide a quick energy boost and may improve athletic performance. 

16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Christopher Bergland
Christopher Bergland is a retired ultra-endurance athlete turned medical writer and science reporter.