Too Much Caffeine Symptoms

Caffeine Overdose and Caffeine Sensitivity Symptoms

The caffeine levels of Starbucks coffee drinks range from 10 mg to 415 mg. Oli Scarff/Getty Images News/Getty Images

What is Caffeine?

Caffeine is a naturally occurring stimulant found in coffee, tea, yerba mate and chocolate (but not found in most "herbal teas"). Caffeine is also isolated as a chemical during the coffee decaffeination process added to caffeinated colas (such as Coke, Pepsi, and Mountain Dew) and certain foods.

How Much Caffeine is Too Much?

In moderation, caffeine is a usually a very safe stimulant that can provide benefits such as alertness and improved mood.

However, too much caffeine consumption can cause a range of side effects. For most people, about 300 mg of caffeine a day is a healthy level of caffeine consumption. That is roughly equivalent to three cups of coffee. However, it is important to recognize that caffeine levels vary widely in coffee, tea and other caffeine-containing substances. (For example, the caffeine levels of Starbucks coffee drinks range from 10 mg to 415 mg.)

Some people are sensitive to caffeine consumption below the "safe" level of 300 mg per day. For more information, see "Caffeine Sensitivity," below.

Caffeine Overdose Symptoms in Adults

Caffeine overdose symptoms vary from person to person and range from moderate (flushed face) to extreme (death), depending on the individual and the level of caffeine consumption. Caffeine overdose symptoms include:

  • Accelerated heartbeat
  • Anxiety and other nervous system issues
  • Confusion
  • Death *
  • Diarrhea
  • Difficulty sleeping, insomnia, restlessness, or issues with passing in and out of consciousness
  • Dizziness
  • Fever
  • Flushed face
  • Gastrointestinal problems
  • Hallucinations and other nervous system symptoms
  • Headaches
  • Increased urination
  • Increased thirst
  • Irregular heartbeat
  • Irritability
  • Jitteriness
  • Muscle twitching/spasms or convulsions
  • Nausea
  • Respiratory problems
  • Vomiting

* Death by caffeine is extremely rare and is often intentional. It would take around 10,000 mg of caffeine (about 100 cups of brewed coffee) to kill someone who weighs 150 pounds.

Caffeine Overdose Symptoms in Infants

Giving infants caffeine is not generally recommended. Most caffeine symptoms for adults are similar for infants, but, because infants weigh much less than adults, the amount of caffeine that will cause them is much lower. Additional caffeine overdose symptoms for infants include low blood pressure and alternation between very tense and very relaxed muscles.

Caffeine Sensitivity

Individuals with health problems or caffeine sensitivity may not be able to safely consume even 200 to 300 mg of caffeine a day. Symptoms of caffeine sensitivity are similar to symptoms of caffeine overdose, but they may begin at much lower levels of caffeine consumption, such as the relatively low level of caffeine in a chocolate bar.

Factors influencing caffeine sensitivity include:

  • Age (Aging usually increases caffeine sensitivity, though children are also sensitive to caffeine, as they generally have much lower weights than adults and have not typically built up a tolerance to caffeine.)
  • Biological sex (Women are sometimes more sensitive to caffeine than men.)
  • Health issues (Anxiety, cardiovascular / heart problems or respiratory problems may increase susceptibility to caffeine sensitivity and overdose.)
  • Irregular caffeine consumption (Regular caffeine consumption increases most people's caffeine tolerances.)
  • Medications (Caffeine can interact with drugs and supplements, including certain antibiotics (notably Ciprofloxacin and Noroxin), Theophylline and echinacea. Potential side effects include amplification of the symptoms associated with excess caffeine consumption and prolonged effects of caffeine.)
  • Weight (Lower weight usually increases caffeine sensitivity.)

If you are experiencing caffeine sensitivity symptoms, you may want to talk with your doctor about your symptoms and any factors that may increase you caffeine sensitivity to determine safe levels of caffeine consumption for yourself.

Reducing / Treating Symptoms from Too Much Caffeine

If you are experiencing serious caffeine overdose symptoms (such as heart palpitations in conjunction with pre-existing cardiovascular issues), do not hesitate to contact poison control or your local emergency services. Read more on what to do for a caffeine overdose for details.

If you are experiencing milder caffeine symptoms (such as jitteriness or restlessness), talk with your doctor or reduce your caffeine consumption level.

If you want to cut down on caffeine consumption, you can avoid some caffeine withdrawal symptoms by cutting back it slowly. If coffee is your caffeine vice, cutting back by half a cup per day is generally recommended. For more on cutting down on caffeine, read how to reduce caffeine intake and check out readers' caffeine reduction tips.