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7 Supplements That Can Make You Nauseous, Doctors Say

These could be causing your chronic nausea.

Developing any new symptom that persists over time is good cause to call your doctor. But nausea can be especially disruptive in your day-to-day life, so you may make that call sooner rather than later. Your doctor will want to rule out underlying conditions such as bowel obstruction, gastroparesis, migraines, peptic ulcers, GERD, and more. However, the good news is that very often, nausea is the result of lifestyle habits that can be fairly easily adjusted. Medications and supplements are among the most common causes of chronic nausea, especially if you take them on an empty stomach.

In fact, there are a handful of supplements that are known to trigger the side effect, often along with other gastrointestinal issues. Wondering if your own supplement regimen could be dialing up your discomfort? These are the seven supplements that could be causing your queasiness, according to doctors and pharmacists.

RELATED: 12 Supplements You Should Never Take Together, Medical Experts Say.


Woman in white blouse holding in hand iron Ferrum supplement capsule and glass of water. Bioactive additive woman pharmacy. Vitamin mineral treatment against anemia. Autumn health care concept

Iron plays a vital role in combating anemia, which occurs when there's a shortage of healthy red blood cells to transport oxygen to the body's essential organs and tissues.

According to HaVy Ngo-Hamilton, PharmD, a pharmacist and clinical consultant at BuzzRx, iron supplements can stimulate the production of red blood cells, effectively reversing iron deficiency in cases where diet alone falls short.

"However, it's important to note that iron supplements, including those found in multivitamins, can lead to unwanted gastrointestinal (GI) side effects such as nausea, stomach pain, and diarrhea," she warns.

Ngo-Hamilton explains that poor iron absorption can make you nauseous and trigger other uncomfortable side effects. "Once taken, the iron supplement will land in the stomach before reaching the small intestine, where absorption occurs. Iron is one of the minerals that does not have excellent absorption," she explains.

"As a result, a small percentage of iron gets absorbed into the bloodstream, while the unabsorbed iron stays in the gastrointestinal tract. This 'left-over' iron isn't GI-friendly since it irritates the lining of the intestines and stomach, leading to nausea, stomach cramps, and diarrhea," she says.

She notes that switching to controlled-release iron supplements might help to reduce nausea and lessen GI discomfort.

Vitamin A

A happy mature woman with short white hair wearing a gray long-sleeved shirt takes a vitamin with a glass of water
Photoroyalty / Shutterstock

Many people take vitamin A to boost their vision health, but it also plays an important role in cellular activities, immune system regulation, bone health, and reproduction, Ngo-Hamilton says.

Because vitamin A is a fat-soluble vitamin, it isn't excreted through urine. "When you take vitamin A daily, and your body doesn't need it, it will be stored in the liver and fat tissue. Excess vitamin A will stay in the body for a long time, leading to toxicity," the pharmacists tells Best Life.

"Nausea is a common sign of too much vitamin A, as is poor appetite, headache, and skin irritation. If you take a multivitamin, talk to your doctor or pharmacist before using additional vitamin A supplements. Your doctor can also recommend a safe dosage of vitamin A," she adds.

RELATED: 5 Supplements That Can Damage Your Kidneys, Doctors Say.


The zinc supplementary white capsule with fresh oyster on block wood

Zinc supplements can help boost your immune system and metabolism, and they're generally well tolerated. However, they can also cause a range of side effects, especially in high doses. These may include indigestion, diarrhea, headaches, nausea and vomiting.

"It is important to not take more than the recommended dose to minimize the risk of nausea," says Jennifer Bourgeois, PharmD, a pharmacy and health expert for SingleCare.

Vitamin C

sliced oranges with vitamin c pills

Vitamin C helps you maintain healthy immune function, bone health, brain function, and more. Most people can get all the vitamin C they need from fruits and vegetables, including citrus fruits, tomatoes, kiwifruits, and more.

"Taking vitamin C supplements is recommended if you don't get enough vitamin C through diet," says Ngo-Hamilton. "However, vitamin C supplements can cause nausea, stomach upset, and diarrhea, especially at higher doses and if you have a sensitive stomach."

The vitamin's acidic nature is the culprit behind unpleasant gastrointestinal distress, the pharmacist says: "Especially at higher doses of vitamin C, the build-up of acid can irritate the lining of the gastrointestinal tract, causing nausea, stomach pain, and diarrhea."

"Taking vitamin C with food or snacks can provide a buffer to alleviate nausea and gastrointestinal distress. Not exceeding 2,000 milligrams (mg) of vitamin C at once can also reduce the risk of nausea," she adds, noting that your doctor or pharmacist can recommend the proper vitamin C dosage.

RELATED: 6 Supplements You Should Never Take If You're Over 60, Doctors Say.


Curcumin supplement capsules, turmeric powder in glass bowl and curcuma root in background.
Microgen / Shutterstock

Turmeric is often used for its beneficial effects on pain, inflammation, and immune function. However, Heather Hinshelwood, MD, an emergency physician and the owner and chief medical officer at The Fraum Center for Restorative Health, says this is another supplement that can make you nauseous, especially in high doses.

"It causes a great deal of GI upset. Think about how we use it in cooking—it adds heat. And some people are taking it in capsule form in very high doses, much higher than what we use in cooking," Hinshelwood tells Best Life.

Ginkgo biloba

Ginko biloba capsules on a wooden spoon and ginko leaf

Ginkgo biloba (or ginkgo) is a popular herbal supplement used to improve symptoms of anxiety, vision health, high blood pressure, and premenstrual syndrome (PMS). Ngo-Hamilton says that while ginkgo biloba is well-tolerated by most people, it can in some cases trigger a vitamin B6 deficiency, which can make you nauseous and cause other GI symptoms.

"Ginkgotoxin is a natural compound found primarily in ginkgo nuts, with a lesser quantity found in the leaves. Ginkgotoxin has a chemical structure similar to that of vitamin B6," she tells Best Life. "Thus, this natural compound has been found to interfere with vitamin B6 activity. The severity of vitamin B6 deficiency caused by ginkgo poisoning varies, depending on the amount consumed, the person's age, and health history."

"By itself, a small to moderate amount of ginkgo biloba can cause nausea. However, with vitamin B6 deficiency caused by ginkgo poisoning, you can experience nausea, vomiting, upset stomach, diarrhea, and potentially a host of other severe symptoms such as seizures and loss of consciousness," the pharmacist says.

RELATED: 7 Supplements to Avoid If You're on Weight-Loss Drugs, Doctors Say.


Customer in pharmacy holding medicine bottle. Woman reading the label text about medical information or side effects in drug store. Patient shopping pills for migraine or flu. Vitamin or zinc tablets.

Finally, if you're feeling chronically nauseous, your daily multivitamin might be to blame, the experts say.

"Some individuals may experience nausea due to the combination of many different ingredients in a multivitamin being introduced into the stomach at one time," Bourgeois tells Best Life. "This may increase stomach acid, thereby inducing nausea. Taking the multivitamin with food can help buffer the stomach acidity and decrease nausea."

Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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