Your body needs vitamins to survive and you're unlikely to overdose on them through diet alone. However, taking vitamin pills can be risky if you don't carefully monitor how much of each vitamin you actually take. This is especially true when it comes to fat-soluble vitamins, which your body stores in its liver and fat for future use.
Vitamin A
It can be easy to take too much preformed vitamin A, called retinol, when you take vitamin pills, according to the Harvard School of Public Health. You are unlikely to overdose on vitamin A if you get it in carotene form from plant foods such as carrots. Check your vitamin pills label to make sure most of the vitamin A in it comes from beta-carotene. Still, you shouldn't have negative effects even taking up to 10,000 micrograms of preformed vitamin A per day; this is over three times your daily-recommended intake. If you exceed the safe amount, you may be at a greater risk of getting a hip fracture and your liver and nervous system may sustain damage.
Vitamin D
A vitamin D overdose may cause symptoms ranging from irritability and nausea to high blood calcium levels, mental retardation, physical retardation and kidney damage, warns the Colorado State University Extension. Yet, vitamin D toxicity is rare even if you take large quantities of it in supplements. You may be more likely to overdose if you have pre-existing health problems such as a kidney or liver condition. Most people should get 600 to 800 IU of vitamin D a day, though your doctor may recommend that you take up to 4,000 IU a day if your body absorbs less sunlight.
Vitamin E
Taking too much supplemental vitamin E can lead to fatigue, nausea, digestive tract problems and excessive bleeding. You may safely take up to 100 IU of vitamin E per day, but you may be at heightened risk of overdose dangers with lower doses if you take a blood-thinning medication or if you take a statin drug for cholesterol problems, according to the Colorado State University Extension.
Vitamin K
No tolerable upper intake has been set for vitamin K, but this doesn't mean you can safely take endless amounts of it. High doses of vitamin K1 or K2 haven't been linked to toxic effects, but synthetic menadione -- vitamin K3 -- and its derivatives may cause problems such as liver damage, jaundice, cell membrane damage and breakdown of blood cells, according to the Linus Pauling Institute at Oregon State University.
B and C Vitamins
Vitamins B and C are water-soluble, meaning your body eliminates them in urine and you need to keep eating them for their benefits. This also means your body is less susceptible to overdosing on them. Still, you may experience temporary problems if you take megadoses of them. For instance, high intake of vitamin C has been linked to stomach distress and high iron levels and megadoses of vitamin B3 may cause flushing and gastrointestinal problems, according to the Institute of Medicine. Ask your doctor to recommend a safe dose based on your individual needs.
Considerations
You shouldn't need to take vitamin pills if you're healthy and your diet is well-balanced. Whole food sources of vitamins tend to offer added perks such as fiber, antioxidants and a complex network of micronutrients. Your doctor may recommend that you take a supplement if your diet is deficient in certain micronutrients or if your body has trouble absorbing certain vitamins. If your doctor does recommend that you take a supplement, find a pill that only contains 100 percent of the Dietary Reference Intakes for most vitamins and be wary of ones that have more than 200 percent, recommends the Harvard School of Public Health. Also, never take more than the recommended dose.
References
- Institute of Medicine: Dietary Reference Intakes: Vitamins
- "Good Housekeeping"; Can You Overdose on Vitamins and Minerals?; Janis Jibrin, M.S., R.D.
- Colorado State University Extension: Fat-Soluble Vitamins; J. Anderson and L. Young; 2008
- Colorado State University Extension: Water-Soluble Vitamins; J. Anderson and L. Young; 2008
- Harvard School of Public Health: Vitamins
- MayoClinic.com: Vitamin D Toxicity: What if You Get Too Much?; Katherine Zeratsky, R.D., L.D.
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