Are mega doses of multivitamins safe?

Vitamins and minerals are naturally occurring substances needed to perform essential chemical activities throughout the body. The exact amount a person needs varies. The body can manufacture some, but most are acquired from food. Vitamin and mineral supplements can be also be taken as a supplement either individually or packaged as a multivitamin.

There are minimum daily values (RDA, recommended dietary allowance) that the body needs, but more is not better. Before you start taking a multivitamin first check with your doctor and pharmacist to see if multivitamins can affect any of your medicines or health conditions.

Many vitamins can cause serious or life-threatening side effects if taken in large doses. And mega doses of vitamin are not recommended during pregnancy (because they can cross over the placenta to reach the fetus) or during breast-feeding (because they can cross over into your milk).

Although unused water-soluble vitamins will end up in your urine, fat-soluble vitamins such as vitamin A are not easily cleared by the body and can be toxic.

Generally, no. Continuous mega-doses of vitamins or minerals can cause short and long-term adverse events. Mega-dosing vitamins refers to the practice of ingesting very large quantities (many times greater than established daily requirements) of vitamins daily with the goal of improving health, longevity or treating a condition or disease state. At high doses, many vitamins (and some minerals) function as drugs, meaning only a qualified physician might recommend high doses as a temporary therapy for a specific condition such as large doses of niacin (vitamin B3) for helping reduce cholesterol. But at these doses, the vitamin works like a drug and as with all drugs, for every action there is a reaction so a doctor must be monitoring. Stay away from mega-dosing anything without qualified professional guidance. the Upper Limit (UL) for a nutrient denotes the highest level of daily intake that would likely pose no risks of adverse health but unnecessary in most cases.
Dr. Michael Roizen, MD
Internal Medicine

NO. While it may seem that taking huge doses of multivitamins would not hurt or may even be better than taking the normal doses, this is just not true. You know the phrase “too much of a good thing.”


While water-soluble vitamins are really hard to overdose on, fat-soluble vitamins like Vitamin D, A, and E can be extremely dangerous in high doses.


Bottom line: Talk with your doctor before taking a multivitamin, no matter how harmless they may seem. Make sure you understand how much of each vitamin you need and how much your vitamin is giving you on top of what you’re most likely getting from food.

Continue Learning about Vitamins



In the United States, the Food and Drug Administration (FDA) regulates vitamin supplements and provides recommended daily amount information. The FDA says that we should pay attention when considering vitamin supplements, because ...

frequently many different vitamins and minerals are combined into one product.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.