Medically reviewed by Patricia Mikula, PharmD
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- Multivitamins often contain concentrated forms of some ingredients like iron, zinc, magnesium, and vitamin C, which can irritate the linings of the stomach, and make you feel nauseous.
- Taking multivitamins, especially more than the required dose, can make your nausea worse.
- Taking multivitamins with food can reduce the risk of nausea.
You are not alone if you have ever taken a multivitamin and felt nauseous. Multivitamins can irritate the stomach lining and cause digestive side effects, especially when you take them on an empty stomach.
Understanding why this happens can help you prevent side effects so that you can take multivitamins comfortably and fill nutritional gaps.
Why Do Multivitamins Make You Nauseous?
Multivitamins can cause nausea due to their ingredients, which may be harsh on the stomach.
Multivitamins often contain concentrated forms of ingredients such as iron, zinc, magnesium, and vitamin C, which can increase stomach acid and irritate the stomach lining, especially when there is no food to act as a buffer.
For example, high doses of iron have been found to increase gut inflammation and alter gut bacteria, increasing the risk of nausea and other gastrointestinal side effects such as cramps, vomiting, diarrhea, and constipation.
Similarly, ascorbic acid, the most common form of vitamin C used in supplements, has very high acidity and may trigger nausea when taken in doses higher than recommended.
Taking multivitamins, especially more than the required dose, can make your nausea worse, especially if you have a sensitive stomach.
Studies have found that exceeding the recommended doses of iron (more than 45 milligrams (mg) per day), zinc (40 mg per day), or vitamin C (2000 mg per day; sometimes 400mg, depending on age) can cause nausea.
Which Ingredients Are More Likely To Trigger Nausea?
Active and inactive ingredients in multivitamins can trigger nausea.
The most common vitamins and minerals in multivitamins known to cause nausea and vomiting, when taken in high doses, include:
- Oral iron
- Zinc
- Vitamin C
- Magnesium
- Vitamin D
- Calcium
Other inactive ingredients in multivitamins, such as binders, fillers, and sweeteners, can also trigger nausea. Some examples include:
- Lactose
- Mannitol
- Sodium Benzoate
- Artificial sweeteners
Multivitamins containing botanicals such as elderberry, cranberry, fenugreek, and echinacea can also irritate the stomach in some people, triggering nausea.
Why Is It Worse To Take Them on an Empty Stomach?
While some vitamins and minerals are better absorbed on an empty stomach, taking multivitamins without food can worsen nausea.
Food often acts as a buffer, or coat, on the stomach, preventing supplements from irritating the stomach lining. Supplements with very high acidity, like vitamin C (ascorbic acid), will worsen nausea if taken without any food.
Taking multivitamins containing fat-soluble vitamins (A, D, E, K) without food, particularly with fat-rich foods like avocados or olive oil, can reduce their absorption and cause stomach discomfort, such as nausea.
How Can You Prevent Nausea?
Here are some steps you can take to prevent nausea when taking multivitamins:
- Choose concentrations below the recommended daily amounts: Avoid taking multivitamins with very high doses of individual supplements. If you are unsure of the recommended upper limit, talk to your pharmacist or healthcare provider.
- Take with food: Taking multivitamins with food can reduce the risk of nausea. Even a simple cracker can help.
- Choose multivitamins with fewer inactive ingredients: Take multivitamins with fewer artificial sweeteners or flavors.
- Consider taking supplements at different times of the day: If you notice taking multivitamins in the morning makes you nauseous, try taking them in the evening.
- Try a different multivitamin: Multivitamins are not all made the same. Some manufacturers may use ingredients that are less upsetting to your stomach. Ask your pharmacist for help choosing a brand that is less likely to cause nausea for you.
Dietary supplements are minimally regulated by the FDA and may or may not be suitable for you. The effects of supplements vary from person to person and depend on many variables, including type, dosage, frequency of use, and interactions with current medications. Please speak with your healthcare provider or pharmacist before starting any supplements.
