Supplements are usually taken to improve health. Doctors and nutritionists warn: You can have too much of a good thing.

Americans have their choice of up to 100,000 different dietary supplements, from vitamins and minerals to herbal options and products promising weight loss and a toned body. Nearly 75% of Americans take at least one supplement, fueling a market that’s worth more than $60 billion. But plenty of people are taking multiple supplements, mixing and matching certain combinations and sharing their so-called supplement stacks online.

That fast and easy access to so many supplements is potentially harmful to your health, raising the risk of unintentionally causing serious health issues like liver and kidney damage, Dr. Mehrosh Naseem, a family medicine and integrative health physician at the Ohio State University Wexner Medical Center, tells Yahoo Life. She compares creating your own supplement stack to trying to diagnose and treat your own health issues — without having a medical degree.

“There can be interactions between supplements and between supplements and medications you may be taking. You can also take more than the maximum safe dose,” Naseem says. “It’s not safe to start taking supplements on your own without talking to a doctor.”

The data supports the potential harm in supplement stacking on your own. Herbal and dietary supplements cause 20% of liver injuries in the U.S., and the problem appears to be getting worse. A 2022 study published in the journal Liver Transplantation suggests that there was an eightfold jump in drug-induced liver failure from herbal and dietary supplements from 1995 through 2020. A 2024 JAMA study found that 15 million Americans use supplements that are potentially toxic to the liver — specifically, turmeric, ashwagandha, black cohosh, garcinia cambogia, green tea and red yeast rice.

“It’s sort of a Wild West out there with supplements,” Dr. David Cutler, a family medicine physician at Providence Saint John’s Health Center in Santa Monica, Calif., tells Yahoo Life.

Most people take a supplement with the goal of improving their health. While many of these seem completely harmless because they’re available over the counter, doctors and nutritionists warn that you can have too much of a good thing.

“There is this perception that supplements are inherently safer than medications, and that's not always the case,” Jessica Cording, a dietitian and author of The Little Book of Game-Changers, tells Yahoo Life. “Supplements can have very powerful effects.”

Why do so many people take supplements?

While some supplements fill an important nutritional gap, such as if you’re low on vitamin D, others reach for these products because of what they promise to do for your overall well-being. “Regardless of your health goals, chances are that a supplement out there claims it can help you,” Laura Natali, a dietitian at NewYork-Presbyterian/Columbia University Irving Medical Center, tells Yahoo Life.

Naseem agrees. “A lot of people go by what the front label reads — things like ‘immune booster’ or ‘gut support,’” she says. But these claims aren’t always supported by research, especially given that supplements are a largely unregulated industry, she says.

“Some supplements have very important benefits,” says Natali. “But many have effects that are unclear and could even cause harm.” She adds: “Dietary supplements are often marketed as a solution for very common yet complex health issues like inflammation, fatigue or aging. And they're frequently promoted by people we admire like celebrities, social media influencers and athletes.” As a result, Natali says there’s a lot of messaging coming at us to buy these products, even if the science behind them isn’t always robust.

Women, who are often targeted by marketing for supplements, are especially vulnerable to serious health consequences from supplements, Naseem says. “We dose differently based on height and weight,” she points out, noting that women on average are smaller than men but will often take the same dose of a supplement as their male counterparts.

Some supplements are easier to overdose on than others

Vitamins can generally be divided into two camps, according to Cording: water-soluble and fat-soluble. Water-soluble vitamins, like vitamins C and B, dissolve in water, while fat-soluble vitamins, like vitamin A, D, E and K, dissolve in fat and are stored in the body’s tissues, Cording explains.

“Generally speaking, you will pee out any excess water-soluble vitamins you take,” Cording says. “But fat-soluble vitamins will build up in the body.” That can cause certain vitamins to potentially hit toxic levels in the body and cause health issues, she says. While some side effects can be mild — abdominal cramps, nausea, diarrhea and headaches — others can be more serious and even fatal, Cording says.

You can also overdo it when it comes to certain minerals. Jamie Alan, an associate professor of pharmacology and toxicology at Michigan State University, tells Yahoo Life that the ones to be mindful of include magnesium, calcium and iron.

• Magnesium. “While this can help with sleep and anxiety, along with many other functions in the body, too much magnesium can cause diarrhea,” Alan says.

• Calcium. It’s possible to take too much calcium, which can cause stomach pain and nausea. “Too much calcium can also impact your kidneys,” Alan says.

• Iron. Many people take iron who have anemia, but too much of the mineral can lead to nausea and stomach issues. “It can also deposit in your liver and heart at higher doses, causing more problems,” Alan says.

While it would be unusual to get too much of any of these from the diet or even a diet plus a recommended dose of a supplement or vitamin, says Alan, “it is easy to take too much when you combine supplements if you are not careful.”

Herbal and dietary supplements are particularly risky, Cutler says. “These are not studied before they come to market. We really don’t know what the effects are,” he says. “Some of these — turmeric, St. John’s wort and ashwagandha — are known to have adverse effects on the liver.” Taking doses that are too high or mixing them with alcohol can cause damage, he says.

Cording agrees. “We’re seeing this a lot with adaptogens, like ashwagandha,” she says. “People may take it in a supplement that contains different adaptogens, and then may have it in a functional beverage. It may also be in your sleep supplement. That can add up.”

How can you safely take supplements?

Experts say this information shouldn’t scare you off of taking a supplement or two — it’s just important to take them under the guidance of a health care provider, especially if you’re taking more than one supplement, and follow the dosage instructions on the label.

“Getting a blood test first is the gold standard because it will give you some clues as to how deficient you may be in a vitamin or mineral and how high of a dose you may need,” Cording says. A health care provider can also take a look at a particular supplement you’re interested in and give their opinion about whether it’s a good choice for you, Naseem says.

“Health care professionals have tons of education on this,” Cording says. “Unfortunately, the general public does not have that same education on dosing and safety, but it’s important information to have.”