Supplement Safety: Understanding Risks and Using Supplements Responsibly

Why Can Supplements Pose Risks?

Dietary supplements are products intended to supplement the diet, not to treat, diagnose, mitigate, prevent, or cure diseases. In the United States, the Food and Drug Administration (FDA) regulates dietary supplements under a different framework than it uses for prescription or over-the-counter medicines. Unlike drugs, supplements do not need FDA approval before they are marketed. Under federal law, manufacturers are responsible for ensuring their products are safe and that their labels are truthful and not misleading, but the FDA only steps in if a problem is reported after the product is on the market.

Because of this regulatory gap, the actual risks of a supplement may be unknown before it reaches store shelves. Side effects are most likely to occur when supplements are taken in high doses, when they are used instead of prescribed medicines, or when many different supplements are combined. Even a product labeled 'natural' can be risky—some botanical products, such as comfrey and kava, can harm the liver.

• Supplements are not intended to replace a balanced diet or to treat illness.
• The FDA does not review supplements for safety or efficacy before they are sold.
• Risk increases with high doses, substitution for prescription drugs, and combining multiple supplements.
• A 'natural' label does not guarantee safety.

Sources: NIH Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH), Annual Review of Pharmacology and Toxicology (via PMC)

Common Side Effects and Adverse Reactions

Supplements can cause a range of side effects, from mild digestive upset to serious organ damage. For example, taking too much vitamin A can lead to headaches, liver damage, reduced bone strength, and, in pregnant women, birth defects. Excess iron can cause nausea and vomiting and may damage the liver and other organs. High doses of calcium supplements, especially in people prone to kidney stones, may increase the risk of developing them.

According to a widely cited analysis, dietary supplements are associated with about 23,000 emergency room visits each year in the United States. Older adults are more likely to be hospitalized after such visits, and symptoms can include chest pain, heart palpitations, dizziness, and vomiting. Research reported by the National Center for Complementary and Integrative Health (NCCIH) indicates that acute liver damage from supplements, while rare, has been reported more frequently in recent years and can be severe, sometimes requiring a liver transplant or leading to death.

• High doses of certain vitamins or minerals can be toxic.
• Common adverse events include gastrointestinal issues, headache, dizziness, and cardiovascular symptoms.
• Liver injury is a rare but serious complication, more often linked to weight-loss and bodybuilding supplements.
• The estimated 23,000 ER visits per year highlight that serious reactions are not negligible.

Sources: NIH Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH), Annual Review of Pharmacology and Toxicology (via PMC), AARP, HelpGuide

Potential Interactions with Medications and Other Supplements

Some supplements can change how your body processes prescription and over-the-counter medications. For instance, vitamin K can reduce the ability of the blood thinner warfarin to prevent clotting. St. John's wort, a popular herbal supplement, speeds the breakdown of many medicines, which may lower their effectiveness—this includes certain antidepressants, birth control pills, heart medications, anti-HIV drugs, and transplant medications. Antioxidant supplements such as vitamins C and E may reduce the effectiveness of some chemotherapy drugs.

Iron is another example: it can interfere with antibiotics, thyroid medication, and bisphosphonates used for osteoporosis. Taking high doses of folic acid can mask a vitamin B12 deficiency, delaying diagnosis. Some supplements contain more than one active ingredient, so interactions can be complex. Always inform your healthcare provider about every supplement you take, including vitamins, minerals, herbs, and other products.

• Vitamin K can interfere with warfarin.
• St. John's wort can speed up drug metabolism.
• Antioxidants may affect chemotherapy.
• Iron interactions with common medications.
• Folic acid can hide B12 deficiency.
• Discuss all supplements with your doctor or pharmacist.

Sources: NIH Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH), AARP, HelpGuide

Who Is at Higher Risk?

Some groups need to be especially cautious about dietary supplements. Many supplements have not been tested in pregnant women, nursing mothers, or children, so safety is often unknown. For example, high doses of vitamin A can cause birth defects. If you are pregnant or nursing, talk with your healthcare provider before taking any supplement.

Older adults face higher risk because they are more likely to take multiple medications and may have reduced kidney or liver function, which affects how supplements are processed. People with chronic conditions such as liver or kidney disease, high blood pressure, or heart conditions may also be more vulnerable. Additionally, products marketed for weight loss, sexual enhancement, or bodybuilding have been found to sometimes contain hidden prescription drugs or unlisted ingredients, posing unexpected risks.

• Pregnant and nursing women: many supplements lack safety data; some can be harmful.
• Children: their bodies are still developing; safety and dosing may differ.
• Older adults: higher risk of interactions and side effects due to polypharmacy and organ changes.
• People with chronic conditions: liver, kidney, or heart disease can alter supplement handling.
• Anyone considering weight-loss or bodybuilding supplements: these have a higher chance of hidden ingredients.

Sources: National Center for Complementary and Integrative Health (NCCIH), AARP, HelpGuide

Recognizing Signs of a Serious Reaction

While most side effects are mild, some reactions require immediate medical attention. Warning signs include chest pain, heart palpitations, dizziness, fainting, difficulty breathing, swelling of the face or throat, severe vomiting, abdominal pain, yellowing of the skin or eyes (signs of liver problems), and dark urine. Any symptom that is sudden, severe, or persistent should be evaluated by a healthcare professional.

It is important to remember that an adverse event may not occur immediately after you start a supplement; it could develop over time. If you experience any unusual symptoms and you take supplements, consider whether they might be related and mention them to your doctor.

• Chest pain, palpitations, or irregular heartbeat
• Dizziness, fainting, or unusual weakness
• Shortness of breath or swelling of face/lips/tongue
• Severe stomach pain, vomiting, or jaundice
• Unexpected bleeding or bruising

Sources: AARP

How to Use Supplements Safely

The wisest approach is to take only supplements you need, at the recommended dose, and to keep your healthcare provider informed. Start with a low dose to see how your body responds, and monitor yourself for any side effects. Do not take more than the label recommends unless a doctor tells you to. Also, be aware that 'more is not better'—high doses can be harmful.

When you are prescribed a new medication, ask your doctor or pharmacist if any supplements you take could interact. And before any surgery, tell your surgeon about all supplements and medicines you use. Some supplements can increase bleeding risk or interfere with anesthesia. Your healthcare team can advise you on what to continue or stop.

• Start low and go slow: begin with the smallest effective dose.
• Monitor your body for any new symptoms.
• Keep a current list of all supplements and medicines.
• Ask a healthcare professional about interactions.
• Do not self-prescribe supplements to treat a medical condition.
• Inform your surgical team about supplements before an operation.

Sources: NIH Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH)

What to Do If You Experience an Adverse Event

If you suspect a supplement is causing a serious reaction, stop taking it and seek medical care right away. For less severe symptoms, contact your healthcare provider. It is also helpful to report any adverse event to the FDA through its Safety Reporting Portal. This helps the agency track safety issues and take action when needed.

When you report, have as much information as possible ready: the product name, manufacturer, dosage, and the date you started and stopped taking it. Also list any other supplements or medicines you use. Your report contributes to the ongoing monitoring of supplement safety.

• Discontinue the supplement immediately if you suspect a serious reaction.
• Call your healthcare provider for guidance.
• Seek emergency care for severe symptoms.
• File a report with the FDA via its Safety Reporting Portal.
• Keep the product label and any packaging for reference.

Sources: National Center for Complementary and Integrative Health (NCCIH), Center for Science in the Public Interest

Safety Checklist

Use this checklist as a quick reference before and while taking any dietary supplement.

• Ask yourself: Do I really need this supplement? Can I get the nutrients from food?
• Talk to your doctor about any medical conditions or medicines you take.
• Read the label: check the Supplement Facts panel and the list of ingredients.
• Choose products from well-known brands and check for third-party testing when possible.
• Avoid products that promise quick fixes or unrealistic results.
• Beware of products marketed as 'legal' alternatives to prescription drugs or anabolic steroids.
• If you have surgery scheduled, discuss all supplements with your surgeon beforehand.
• Report any unusual symptoms to a healthcare professional promptly.

Sources: NIH Office of Dietary Supplements (ODS), National Center for Complementary and Integrative Health (NCCIH), AARP, Center for Science in the Public Interest