Understanding Dietary Supplements: A Beginner's Guide

Faith Coleman

Medically reviewed by Faith Coleman, University of New Mexico School of Medicine on August 30th, 2026.

Published on May 26th, 2023.

Key takeaways

  • The FDA doesn't require safety testing before supplements reach market—unlike prescription drugs, manufacturers only need to notify the FDA 75 days before selling a new substance.

  • Vitamin D toxicity can occur with doses above 10,000 IU daily for months, causing kidney damage and calcium buildup in arteries.

  • Third-party certifications from NSF, USP, or ConsumerLab verify that products contain stated ingredients without harmful contaminants like heavy metals or pesticides.

  • Certain combinations have adverse interactions: calcium blocks iron absorption by 60%, while St. John's wort reduces oral contraceptive effectiveness and blood thinner effects.

  • Adults taking 4+ supplements have a 65% higher risk of adverse reactions, particularly those over 65 who metabolize compounds more slowly.

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If you're looking to improve your health, you may be considering taking dietary supplements. But with so many options available, it can be overwhelming to know where to start. This beginner's guide will help you understand the basics of supplements, including what they are, how to take them safely, and how to choose quality products.

For individuals who eat a balanced diet and do not have a medical condition that impairs nutrient absorption or increases nutrient requirements, routine dietary supplements are rarely necessary, and their health‑enhancing effects are unproven or minimal in well‑nourished adults. This article is not an endorsement nor encouragement of taking dietary supplements. This information is for educational purposes only.

What Are Dietary Supplements?

Dietary supplements are products that contain vitamins, minerals, herbs, botanicals, enzymes, amino acids, or other dietary ingredients. They come in various forms, such as pills, capsules, tablets, powders, or liquids, and are intended to supplement your diet. It's important to remember that supplements are not a substitute for a healthy diet and lifestyle.

Talking to Your Doctor About Supplements

Before starting any supplement regimen, it's crucial to talk to your doctor. While supplements are available over-the-counter, some can interact with medications or have side effects. This is especially important if you are pregnant, nursing, have a health condition, or are preparing for surgery. Your doctor can help you determine if a supplement is right for you and provide guidance on dosage and duration.

When discussing supplements with your doctor, be sure to ask questions such as:

  • Are there any studies showing that this supplement is safe and effective?
  • What are the potential side effects?
  • Will this supplement interact with any medications or other supplements I'm taking?
  • Is this supplement safe for me to take given my health condition?

How to Take Supplements Safely

When taking supplements, it's essential to follow the directions on the package and your doctor's instructions. Keep a list of all the supplements and medications you're taking, including the dosage and time of day. This can help you avoid accidentally taking too much and allow you to track any side effects. Share this information with your doctor at each visit.

Choosing Quality Supplements

Not all supplements are created equal. Manufacturers are not required to test their products for safety and effectiveness before selling them. To ensure you're getting a quality product, look for supplements that have been tested and approved by reputable organizations such as U.S. Pharmacopeia, ConsumerLab, or NSF International.

Be wary of supplements that make overhyped claims like "miracle cure" or "completely safe." If a claim seems too good to be true, it probably is. Check the FDA's website to see if a supplement has been recalled, and don't hesitate to contact the manufacturer with any questions about their products.

Understanding Supplement Labels

Supplement labels can be confusing, but understanding a few key terms can help. "Standardized" means that the manufacturer ensures consistent production, with the same ingredients and concentrations in each batch. "Proprietary blend" refers to a unique combination of ingredients used by one manufacturer.

You may also see "RDA" (Recommended Dietary Allowance) or "DV" (Daily Value) on supplement labels. The RDA is the amount of a nutrient you should get each day based on your age, gender, and other factors. The DV represents how much of a nutrient the supplement provides in relation to a total daily diet.

For most supplements RDA has not been established and suggested dosing for the advertised effect is speculative.

Reporting Side Effects

If you experience any side effects from a supplement, stop taking it immediately and report it to your doctor. You may also call the Poison Help line at 800-222-1222. You can also report side effects directly to the FDA by calling 800-FDA-1088 or visiting www.fda.gov/medwatch.

By understanding the basics of dietary supplements and working closely with your healthcare provider, you can make informed decisions about which products may benefit your health.

The Bottom Line

Choose third-party tested products and never exceed recommended doses without medical supervision. Always inform your doctor about every supplement you take since interactions with medications can be serious. If you're experiencing unusual symptoms after starting any supplement, Doctronic can help you determine if it's related and what steps to take.

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