Good Health Reviews is not medical advice. Everything on this site is general information. We’re not doctors, nutritionists, pharmacists, or other health professionals, and nothing here is meant to diagnose, treat, cure, or prevent any disease.
Using this site doesn’t create a doctor-patient relationship or any other professional relationship.
About dietary supplements
Unlike prescription drugs, dietary supplements in the United States don’t have to be approved by the FDA for safety or effectiveness before they’re sold. The companies that make them are responsible for making sure their products are safe and their labels are truthful.
Statements about supplements on this site have not been evaluated by the Food and Drug Administration. The products we discuss are not intended to diagnose, treat, cure, or prevent any disease.
“Natural” doesn’t automatically mean safe. Anything strong enough to have an effect on your body can also have side effects or interact with other things you take.
Talk to your doctor first
Please check with your doctor or pharmacist before starting any supplement, especially if you:
- are pregnant, trying to get pregnant, or breastfeeding
- take any prescription or over-the-counter medication
- have a medical condition, such as diabetes, heart disease, high blood pressure, or a thyroid, kidney, or liver problem
- have surgery coming up
- are buying for someone under 18, or for an older adult who takes several medications
Common interactions to know about
These are examples, not a complete list. Your pharmacist can check your specific combination of medications and supplements.
- Blood thinners (like warfarin): ginkgo, garlic, fish oil, vitamin E, and turmeric may raise bleeding risk, and vitamin K can make warfarin less effective.
- Diabetes medications: ingredients marketed for blood sugar, such as berberine, cinnamon, chromium, or bitter melon, may add to the effect of your medication and push blood sugar too low.
- Thyroid medication: iodine and kelp can affect thyroid function, and calcium or iron taken at the same time can reduce how well levothyroxine is absorbed.
- Antidepressants, birth control, and many other drugs: St. John’s wort can make a long list of medications less effective.
- Heart and blood pressure: stimulants such as caffeine and yohimbine, and caffeine-containing extracts like green tea or guarana, can raise heart rate and blood pressure.
- Lab tests: high-dose biotin, common in hair, skin, and nail products, can throw off some blood test results, including thyroid and heart tests. Tell your doctor if you take it.
The FDA has also found hidden drug ingredients in hundreds of products sold as supplements, mostly ones promoted for weight loss, sexual enhancement, and bodybuilding. Take extra care with products in those categories.
About the research we cite
We summarize published studies on individual ingredients. A study on an ingredient isn’t a study on the finished product. The dose in a product may be different from the dose that was studied, and results seen in a study group don’t predict results for any one person.
Health programs and guides
Some of the products we cover are programs, e-books, or audio sessions. The same rules apply. They’re not a substitute for care from a qualified professional, and please don’t stop or change a treatment because of something you read or heard in one.
If something doesn’t feel right
If you notice side effects, stop taking the product and contact your doctor. For a medical emergency, call 911 or your local emergency number.
You can also report a bad reaction to a supplement to the FDA through its Safety Reporting Portal. The FDA explains the steps on its page about how to report a problem with dietary supplements.
Questions
We can’t answer personal medical questions, but if something on one of our pages is unclear or looks wrong, email contato@webflag.com.br. See also our How We Review and Affiliate Disclosure pages.
Last updated: November 2026.