A multivitamin is meant to supplement a fairly balanced diet to ensure that your body gets all of the minerals and vitamins it needs. However, if you are experiencing a symptom such as diarrhea after taking one, you could be having a reaction, may have consumed too much of it or may have taken it with the wrong combination of foods or drink. Check with your doctor to see if any of your prescribed medications should not be taken in conjunction with a specific multivitamin.
Overdose
Iron and calcium in overly large doses are particularly dangerous. The only way you would overdose on these with a multivitamin is if you took more than the dosage suggested or got one that had excess in it through a manufacturing process error. According to Drugs.com, diarrhea is one reaction you can have if you have consumed too many multivitamins or too much of a mineral contained in the pill. Only take the recommended dosage of the vitamin and follow instructions on the package about how to take it for best results.
Side Effects
If you recently started taking a new brand or type of multivitamin, it may cause diarrhea. According to online health study database eHealthMe.com, diarrhea is a side effect of multivitamins -- of 2,735 individuals, 175 had diarrhea with chronic use of a multivitamin. However, as Katherine Zeratsky and Jennifer Nelson, registered dietitians on Mayo Clinic's website, state, there is no process to include data on vitamins' side effects for individuals.
Food and Drink Consumption
Consume a multivitamin after you have some food in your stomach. Keep in mind that grapefruit juice can interfere with multivitamin absorption and can lead to side effects, including diarrhea. According to USPharmacist.com, calcium -- whether in food or as a supplement -- interacts with vitamins and medications. Therefore, avoid dairy products when taking your multivitamin.
Pregnancy
Some pregnant women may have diarrhea from taking vitamins. Pregnant women are prescribed prenatal vitamins that have higher amounts of certain ingredients, such as folic acid. If you experience diarrhea while taking a prenatal vitamin, ask your doctor if you can switch to another kind.
