Taking a multivitamin to make sure you meet the minimum requirements for essential vitamins and minerals is fine for most healthy people, but taking more than one multivitamin per day is not, unless you choose a multivitamin that is formulated to be taken twice a day. Taking two multivitamins can put you over the tolerable upper intake levels for certain vitamins and minerals and cause dangerous toxicity symptoms.
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Multivitamins often contain all of the essential vitamins, as well as a number of minerals, including calcium, manganese, iodine, iron, copper, chromium, molybdenum, zinc, potassium and magnesium. If there isn't a recommended dietary allowance or a daily value for a vitamin or mineral, you don't need it in your multivitamin since it hasn't been proven necessary for good health, according to the Linus Pauling Institute.
Consuming too much of almost any vitamin or mineral can cause toxicity, but fat-soluble vitamins A, D, E and K, as well as minerals, especially iron, are most likely to cause toxicity. Taking more than the recommended one multivitamin per day may cause you to exceed the tolerable upper intake level for these or other vitamins and minerals, especially if you do so for an extended period of time.
Toxicity symptoms vary depending on the severity of the toxicity and the vitamin or mineral causing the symptoms. These symptoms can include increased urine or cloudy urine, irritated eyes, light sensitivity, cracked and dry lips and skin, itching, rash, flushing, hair loss, muscle weakness or pain, bone or joint pain, irregular or rapid heartbeat, vomiting, nausea, diarrhea, constipation, weight loss, stomach pain, headache, irritability, fatigue, fainting, moodiness, seizures and confusion.
There is no need to take more than one multivitamin. If you are concerned about your vitamin and mineral levels, check with your doctor. Should you be deficient in a particular nutrient, he can prescribe the proper supplements. Most people do not even need to take a multivitamin, according to a story on MSNBC. Supplements are not as well regulated as drugs, so some multivitamins may also be contaminated with toxic substances such as lead, or they may contain different amounts of nutrients than those listed on the label.