Before Starting a New Supplement: Questions About Evidence, Interactions, and Quality

By MedicalFoundationOfNC.org Research Team

Before you start a new supplement, ask five things: what you want it for, what kind of evidence backs that use, what the label says you would actually take, whether an independent group has tested the product, and whether it could interact with your medicines or health situation. The checklist below turns those questions into a card you can fill in for any product. None of it requires buying anything.

This is general education, not medical advice. It does not replace a conversation with your doctor, pharmacist, or dietitian. See our medical disclaimer for details.

Why a Supplement Needs Its Own Checklist

Supplements are regulated differently from prescription and over-the-counter medicines. According to the NIH Office of Dietary Supplements (ODS), medicines must be approved by FDA before they are sold, but supplements do not require that approval. ODS also states that FDA does not determine whether dietary supplements are effective before they are marketed.

FDA explains that manufacturers and distributors are responsible for evaluating the safety and labeling of their products before marketing, and that FDA can take action against an adulterated or misbranded product after it reaches the market. In practice, much of the checking falls to you and your health care team before you start.

The Supplement Due-Diligence Card

Copy these six items into a note and fill them in for each product you are considering. If you cannot fill one in, that is useful information.

1. Intended Use

Write one sentence: “I want to take this for ______.”
Ask your provider whether you need a supplement at all. ODS says health care providers can help you determine which supplements, if any, might be valuable for you.
ODS notes that some supplements can help people get adequate amounts of essential nutrients if they don’t eat a nutritious variety of foods, but that supplements cannot take the place of a varied diet.
If the goal is to treat a health condition, ODS advises consulting your health care provider before taking a supplement for it.

2. Evidence Type

The first three bullets are general reading tips from our editorial team, not findings from the government sources cited in this article.

Identify what kind of evidence is being offered: studies in people, studies in animals or lab cells, or only traditional use and marketing statements.
Check whether the evidence is about the same ingredient, in a similar amount, for the same use you have in mind.
Be cautious when a product cites research on an ingredient but the label shows a much smaller amount than what was studied.
ODS gives examples of supplements with support for specific uses, such as calcium and vitamin D for keeping bones strong and folic acid to decrease the risk of certain birth defects. It also says many other supplements need more study to determine if they have value.
For category-specific examples, see our guides on blood sugar supplements and brain and nerve health supplements.

3. Serving Amount and Label Completeness

Look for a Supplement Facts label. ODS says it lists the active ingredients, the amount per serving, and other ingredients such as fillers, binders, and flavorings.
Check that each active ingredient shows a specific amount.
Remember that the manufacturer suggests the serving size, and your health care provider might decide a different amount is more appropriate for you.
Add up what you already get. ODS notes that vitamins, minerals, and other ingredients are added to foods such as breakfast cereals and beverages, so you may be getting more than you think, and more is not always better.
Count how many products you take. ODS says side effects are most likely if you take high doses, take supplements instead of prescribed medicines, or take many different supplements.

4. Third-Party Testing and Quality Signals

Ask whether the product carries a seal from an independent testing organization. ODS lists ConsumerLab.com, NSF International, and U.S. Pharmacopeia as examples of organizations that offer quality testing. ODS notes that listing them is not an endorsement.
Understand what a seal means. According to ODS, it indicates the product was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants. It does not guarantee the product is safe or effective.
Know what Good Manufacturing Practices (GMPs) are. FDA has established GMPs that companies must follow to help ensure the identity, purity, strength, and composition of supplements, and FDA periodically inspects facilities. Following GMPs is a manufacturing standard, not evidence that a product works.

5. Interactions and Personal Risk Factors

Write down every prescription, over-the-counter medicine, and supplement you use. ODS offers a printable form, My Dietary Supplement and Medicine Record, for the product name, dose, how often you take it, and why.
Know that interactions are real. ODS gives examples: vitamin K can reduce the ability of the blood thinner warfarin to prevent clotting; St. John’s wort can speed the breakdown of many medicines and reduce their effectiveness; and antioxidant supplements such as vitamins C and E might reduce the effectiveness of some cancer chemotherapy.
Do not assume “natural” means safe. ODS points to botanical products such as comfrey and kava that can harm the liver.
Ask specifically about surgery. ODS says some supplements can increase the risk of bleeding or change your response to anesthesia if taken before surgery.

6. Stop-and-Ask Triggers

Pause and talk with a doctor, pharmacist, or dietitian before starting, or contact your provider if you already take the product, when any of these apply:

You take prescription medicines, or you are thinking of using a supplement in place of one. ODS advises getting your provider’s approval before taking supplements in place of, or in combination with, prescribed medicines. As our medical disclaimer also says, do not change or stop a prescribed medicine without your physician’s guidance.
You are pregnant or nursing. ODS advises caution about supplements beyond a standard prenatal supplement.
The supplement is for a child. ODS says to be careful about giving supplements to a child unless their health care provider recommends them.
You have a scheduled surgical procedure.
You want to use the supplement to treat a health condition.
You think you have had a bad reaction. ODS says to let your health care provider know. FDA says that if a supplement may have caused a serious reaction or illness, you should immediately stop using it and file a report through the Safety Reporting Portal, as described on FDA’s reporting page. ODS also suggests telling the manufacturer using the contact details on the label.
Symptoms feel severe or urgent. As general safety practice, seek emergency care rather than waiting for an appointment.

Reading Label Claims Carefully

Supplement labels may say a product “supports” a body part or function, such as heart health or the immune system. ODS explains that these claims must be followed by a statement that FDA has not evaluated them and that the product is not intended to diagnose, treat, cure, or prevent any disease. Supplements are not medicines, so a claim that a product treats or cures a disease is a red flag. ODS notes that the federal government can take legal action against companies that make false or deceptive statements, promote supplements as treatments or cures for diseases, or sell unsafe products.

What You Can Do Next

Fill in the six-item card for the product you are considering.
Fill out the ODS medicine and supplement record and bring it to your next appointment or to a pharmacist.
Ask your provider the four questions ODS suggests: What are its potential benefits for me? Does it have any safety risks? What is the proper dose to take? How, when, and for how long should I take it?
Check FDA’s dietary supplements page for recalls and safety alerts. ODS notes that you can subscribe to FDA notices of recalls, market withdrawals, and safety alerts.
If you decide not to take the supplement, that is a reasonable result of this process.

About This Article

MedicalFoundationOfNC.org is an independent health and wellness publication. It is not affiliated with The Medical Foundation of North Carolina, Inc., UNC Health Foundation, or the University of North Carolina at Chapel Hill. This domain was previously associated with that organization. This article does not recommend any specific product and contains no affiliate links. Some other pages on this site do contain paid links, which are disclosed on those pages. Learn more about how we review content and read our standards and disclosures.

Sources

NIH Office of Dietary Supplements, Dietary Supplements: What You Need to Know (Consumer fact sheet). The page shows an updated date of January 4, 2023.
NIH Office of Dietary Supplements, My Dietary Supplement and Medicine Record. Linked from the fact sheet; the form itself was not opened.
U.S. Food and Drug Administration, Dietary Supplements. The page shows content current as of October 1, 2024.
U.S. Food and Drug Administration, How to Report a Problem with Dietary Supplements.