People use herbal supplements because they want to feel better, stay healthier or improve their quality of life. Some get the hoped-for benefit. But for others, a supplement that they expected to be helpful turns out to be harmful instead.

In fact, there is scant science on the safety of a number of herbal products. Unlike medications, supplements do not need FDA approval to be sold. Yet some can have strong effects on the body. At times, they may cause serious symptoms or dangerous reactions.

Things that increase your risk

The risk for unwanted effects is higher if you:

• Use more than the recommended amount of an herbal supplement.
• Take a supplement along with prescription or over-the-counter medications.
• Combine two or more supplements.
• Use a supplement in place of medication recommended by your healthcare provider.

Herbal products labeled “all natural” are not necessarily safer. In fact, they may not have been refined to remove components that could be harmful.

Health booster or risky remedy?

Be safe, not sorry. Talk with your provider before using any herbal supplement. Below are a few examples of why that’s crucial:

• White mulberry leaf was cited by the coroner in the high-profile death of a congressman’s wife. The coroner’s report said that she died of dehydration after consuming the herb.
• Ginkgo, aspirin and warfarin (a blood thinner) all help keep blood from clotting. Taking any two of them together raises the risk for internal bleeding or stroke.
• St. John’s wort can weaken the effects of many critical medications. That includes ones prescribed for depression, heart disease, cancer, seizures, HIV and birth control.
• Kava supplements have been tied to liver damage, which may be severe or even fatal. Long-term use at high doses may also cause dry, flaky, yellowish skin.
• Comfrey is another herb that can seriously harm the liver when taken by mouth.
• Goldenseal may affect how the body processes medications. One study found that it lowered levels of metformin (a diabetes medicine).

Treat herbal supplements with the respect they deserve. If you take a supplement and experience unwanted effects — such as itching, persistent vomiting or severe belly pain — stop using it immediately and seek medical care.