According to the U.S. Food and Drug Administration (FDA), approximately 75% of all Americans take at least one dietary supplement. That’s no surprise if you’ve checked out TikTok lately–people are taking pills, drink mixes, and gummies with the hopes they’ll solve everything from nutrient deficiencies to curing acne. In many videos, people are seen stacking supplements, thinking that combo platters of products may boost their health. But you can have too much of a good thing; knowing the signs that you’re taking too many vitamins or supplements may help you from doing some serious damage.

“People think of supplements in the same way they do fruit,” says Robert J. Fontana, M.D., professor of medicine at University of Michigan Medical School in Ann Arbor. “They think, cranberries or grapes can’t make me sick, so if I consume more of them, I’ll get healthier.”

Meet the experts: Robert J. Fontana, M.D., professor of medicine at University of Michigan Medical School in Ann Arbor; Cindy Reuter, N.D., M.S.O.M., M.P.H., LA.c., medical director of integrative medicine at Dartmouth Health Alice Peck Day Memorial Hospital in Lebanon, NH; Pieter Cohen, M.D., associate professor of medicine at Harvard Medical School and leader of the Cambridge Health Alliance Supplement Research Program in Cambridge, MA; Olivia Thomas, M.S., R.D., L.D.N., director of nutrition innovation and implementation at Boston Medical Center in Boston, MA.

Yet taking too much of any over-the-counter supplement you select on your own, either by itself or in combination with others or medications, comes with risks. Before you add anything to your routine, make sure it’s safe for you. “The number one thing to do is to talk to your doctor,” says Pieter Cohen, M.D., associate professor of medicine at Harvard Medical School and leader of the Cambridge Health Alliance Supplement Research Program in Cambridge, MA.

The FDA doesn’t regulate supplements the same way it does “traditional” medication or food. Instead, supplement companies are responsible for testing their products for safety–something that’s hard to confirm. “You don’t know the quality of the supplement,” Dr. Cohen continues. “Often, supplements are not accurately labeled. Avoid supplements with labels that suggest they’ll do anything.”

Wondering if your supplement stack is worth continuing, or potentially harming your health? Here, experts explain the signs and symptoms of taking too many vitamins and supplements.

What happens if you take too many vitamins and supplements?

To answer this question, you have to know what supplements are really intended for. “Supplements are commercial products marketed for health, but they are not medications,” says Olivia Thomas, M.S., R.D., L.D.N., director of nutrition innovation and implementation at Boston Medical Center in Boston, MA. “The most important thing is to know why you are considering the supplement in the first place. Supplements should fill a specific nutrient gap, not replace a balanced diet or act as a shortcut to better health.”

Some with certain medical conditions should avoid certain supplements altogether. “Be extra cautious if you’re on any medications and/or already using other supplements, if you have liver, kidney, or heart problems, if you’re undergoing cancer treatment, if you’re on immune-modifying drugs or blood thinners, or if you’re pregnant, breastfeeding or trying to conceive,” says Cindy Reuter, N.D., M.S.O.M., M.P.H., LA.c., medical director of integrative medicine at Dartmouth Health Alice Peck Day Memorial Hospital in Lebanon, NH.

Signs you’re taking too many vitamins and supplements

There are a variety of signs that may show your body is holding onto too high of a dose. “It’s important to remember that water-soluble vitamins, such as vitamin C and the B-vitamins, are generally excreted in urine when taken in excess, while fat-soluble vitamins, such as A, D, E, and K, can build up in the body and pose a higher risk of toxicity if overused,” says Thomas. “Minerals and other supplements can also carry risks, since they play critical roles in many body systems and even small imbalances can disrupt normal function.”

Depending on the supplement or combination of supplements, you may experience a wide range of symptoms. “Taking too much can sometimes look like vague, everyday symptoms,” Thomas explains. “Warning signs include bright or discolored urine. digestive issues such as nausea, diarrhea, constipation, or abdominal pain. Neurological symptoms like headaches, dizziness, tingling in the hands or feet, or trouble sleeping can also be a signal. Other unexplained changes in health, such as fatigue, hair loss, changes in skin tone, or abnormal lab results like elevated liver enzymes or kidney function issues, should also be taken seriously.”

Some signs are specific to certain supplements. If you’re concerned you’re taking too many vitamins or supplements, consult your physician, stat. Wondering what symptoms to look for? Here are strong indicators that your supplement(s) may be doing more harm than good.

1. Heart palpitations or chest pain

Seek medical attention if you experience any cardiac symptoms, particularly while taking a supplement. “These products can have a lot of caffeine,” says Dr. Fontana. “They can raise your blood pressure.” Whether you have an underlying heart condition you either know or don’t know about, it’s important to get these kinds of symptoms checked out. Also, Dr. Fontana notes that if you take calcium channel blockers to lower your blood pressure, herbal supplements may interact.

2. Skin irritation

“Rashes or allergy-like reactions may indicate you’re taking too much of a supplement,” says Reuter. A study found that allergic contact dermatitis was a possible side effect of taking any vitamins except for vitamin B2 and vitamin B9.

3. Dark urine with yellowing of your skin

Again, bring these symptoms to your healthcare provider’s attention right away. “Although it’s rare, your supplements could be causing a liver injury,” explains Dr. Fontana.

4. Dizziness

This can indicate you’ve taken too much iron. “Excess iron intake can lead to liver toxicity,” explains Sue-Ellen Anderson-Haynes, M.S., R.D.N., C.D.C.E.S., spokesperson for the Academy of Nutrition and Dietetics and owner of 360Girls&Women and B.E.A.T. Gestational Diabetes. “Signs of iron overload may also include low blood pressure, a metallic taste in your mouth, and convulsions.” Another reason to seek medical help quickly.

5. GI problems.

Mayo Clinic reports that fiber supplements may cause bloating and gas, while too much vitamin C may result in diarrhea, upset stomach, and vomiting.

A really good rule of thumb: the goal of supplements is to enhance nutrition, but you shouldn’t notice that it’s happening. “No supplement should make you start to feel good or bad,” says Dr. Cohen. Any physical change you experience indicates you might need to rethink taking it.

Which vitamins and supplements should you never take together?

A number of combinations should be avoided. “Calcium and iron compete with each other for absorption, so they should not be taken at the same time,” says Thomas. “Also, iron and calcium can interfere with the absorption of thyroid hormone replacement medications like levothyroxine. Vitamin K can counteract blood thinners such as warfarin if taken in high doses. Plus, St. John’s wort can also interfere with antidepressants.”

Combining vitamins may also be a hazard, such as “multiple preparations with B vitamins, vitamin D, and vitamin A,” says Reuter. She also notes that additional combinations to avoid include “multiple supplements with ingredients that affect bleeding and/or blood clotting, multiple supplements that have stimulating effects like preparations for focus, alertness, weight loss, and energy, and drug-supplement-herb combos.”

Long-term treatments may also be negatively affected by herbal supplements. A 2025 study found that older patients undergoing cancer treatment experienced adverse reactions if while taking red yeast rice, red coneflower, turmeric, and cannabis.

The bottom line

If you’re already taking supplements, fill up a bag with your bottles and bring them to your healthcare provider. “Tell your doctor what you’re taking,” says Dr. Fontana. “Patients are often reluctant to reveal the supplements they’re taking because they think their doctor will think they don’t trust the care they’re being given. Be honest and open–doctors just want to help you. We’re not going to judge you.” Transparency means safety when it comes to supplements–the more your doctor helps you, the better your health will be.

Dietary supplements are products intended to supplement the diet. They are not medicines and are not intended to treat, diagnose, mitigate, prevent, or cure diseases. Be cautious about taking dietary supplements if you are pregnant or nursing. Also, be careful about giving supplements to a child, unless recommended by their healthcare provider.

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