Caffeine is a natural substance that can be found in plant-based products such as tea, coffee and cocoa beans. Caffeine is also available in a man-made form and is commonly added to soft drinks and medications. Although caffeine is legal and widely used -- and it rarely causes serious health problems in small amounts -- excess caffeine intake may lead to serious health complications.
Initial Symptoms
You may begin experiencing adverse effects of excess caffeine intake as soon as you exceed about 500 to 600 milligrams of caffeine per day, according to MayoClinic.com. This is equivalent to about three to six 8-ounce cups of brewed coffee, depending on how strong the brew is. Symptoms of excess caffeine intake can include restlessness, stomach upset, rapid pulse, anxiety and tremors in the muscles.
When to Get Help
Increasingly severe symptoms generally correspond with increasing levels of caffeine intake. Symptoms such as breathing troubles, dizziness, fever, hallucinations, irregular heartbeat, vomiting, convulsions and changes in alertness call for medical intervention. If you believe that you or anyone you know has ingested a seriously high dose of caffeine, call for immediate medical help or get in touch with the National Poison Control Center, MedlinePlus recommends.
A Lethal Dose
Although a fatal overdose of caffeine is rare, massive doses of caffeine can be lethal. A fatal dose is generally more than about 10 grams, which would equal about 80 to 100 cups of coffee one right after the other, according to the University of Washington Neuroscience for Kids website. In a 2005 “Forensic Science International” report, the New Mexico Department of Health Toxicology Bureau noted it had seen only two cases of fatal caffeine overdose over about 12 months, and that fatal cases typically involved consuming in excess of about 5 grams. You would be much more likely to consume a fatal dose of caffeine if you took caffeine pills or caffeine in its powder form.
Considering Your Intake
Most people can have a moderate 200 to 300 milligrams of caffeine per day, according to MayoClinic.com. As a reference point, a cup of iced tea contains about 70 milligrams of caffeine, brewed coffee can contain up to about 200 milligrams of caffeine and caffeinated soft drinks can contain up to 55 milligrams of caffeine. You will have more symptoms with less caffeine if you are sensitive to its effects. For instance, children, smaller adults, older adults, pregnant women and people who aren’t used to having caffeine are more likely to be sensitive. Ask your doctor to guide your caffeine intake if you are expecting a child or if you have an underlying health condition.
References
- MedlinePlus: Caffeine Overdose
- MayoClinic.com; Caffeine – How Much Is Too Much?; March 2011
- University of Illinois McKinley Health Center: Caffeine
- MedlinePlus: Caffeine in the Diet
- University of Missouri Extension; What’s Wrong With Caffeine?; Candance Gabel, M.S., R.D., L.D., et al.
- University of Washington Neuroscience for Kids; Effects of Caffeine on the Nervous System; Eric H. Chudler, Ph.D.
- “Forensic Science International”; Fatal Caffeine Overdose: Two Case Reports; S. Kerrigan, et al.; October 2005
- National Poison Control Center: Emergency Number
- MayoClinic.com; Caffeine Content for Coffee, Tea, Soda and More; October 2009
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