Supplements on GLP-1s: What to Take, What to Skip, and How to Stay Safe

If you're taking a GLP-1 medication like Wegovy or Zepbound, your social media feed is probably full of supplement ads. They can feel endless, urgent, and confusing.

As an obesity medicine physician, I hear the same question from patients all the time: "Do I need supplements while I'm on a GLP-1?"

The honest answer is that some supplements can be helpful, but many people don't need most of what they're being sold. My goal is to help you spend less money, take fewer unnecessary pills, and make safer choices while your appetite and portion sizes are changing.

Supplements vs. Medications: Why the Difference Matters

Prescription medications, including GLP-1s, are prescribed and monitored by a clinician. They go through FDA oversight and quality control and have been shown to be safe and effective when used appropriately.

Supplements don't work that way. They can be sold at supermarkets, gas stations, and online stores like Amazon, and they're heavily marketed through affiliate links and social media. Manufacturers aren't required to have a third party test their products.

That means quality varies. A label may not match what's actually in the bottle, and some products contain additives you didn't choose.

How to Choose a Quality Supplement Brand

Look for brands that go the extra mile and pay an independent organization to verify their product. Three common third-party seals to look for:

USP
NSF
ConsumerLab

Check the label and the company's website. If you can't find evidence of third-party testing, consider a different brand.

"Natural" Does Not Mean Safe

It's easy to assume that if something is sold at a grocery store, it must be safe. That isn't true. Even water can be dangerous in very high amounts, and plenty of natural substances, from poisonous mushrooms and berries to opium, can cause serious harm.

Here's how to be an educated supplement consumer:

Tell your doctor or pharmacist about everything you take. Supplements can interact with prescription medications and with each other, making them less effective or more potent. You may need medication adjustments or monitoring.
More is not better. Higher doses can backfire.
Remember your organs. Your liver and kidneys have to process everything you swallow. Too many products can strain them, so liver and kidney function sometimes need to be monitored in people taking a lot of supplements.

Supplements I Commonly Consider in Obesity Medicine

This is not a list of things you should all be taking. It's a shortlist of supplements I consider, depending on the person.

1. Multivitamin

If you're eating smaller portions, following a nutrition plan, or eating less on a GLP-1 (especially when you're first starting), a multivitamin can help cover the nutritional bases.

If you work with a dietitian or obesity medicine physician and eat a wide variety of fruits, vegetables, nuts, seeds, and animal products consistently, you may not need one. Many of us don't hit those goals every day, so a multivitamin is worth considering.

2. Prenatal Vitamin

If you could become pregnant and you're not using birth control, a prenatal vitamin is a smart choice. It's recommended to start at least a month before conceiving, and about half of pregnancies in the U.S. are unplanned. Taking one protects both your health and a future baby's health.

3. Vitamin D

Many people can benefit from vitamin D. The Endocrine Society released new guidelines within the last year that, for most people, no longer recommend screening for vitamin D deficiency and suggest simply starting supplementation. Up to 5,000 IU daily can be used to ensure adequate intake.

You're at higher risk for low vitamin D if you:

Work indoors most of the day
Wear sunscreen outdoors (which you should, to protect against skin cancer)
Have darker skin

Vitamin D supports energy levels, healthy hair growth, bone health as we age, and normal hormone development, since vitamin D is required for hormone synthesis. There is also some evidence that it may slow or delay progression from prediabetes to type 2 diabetes. If you have insulin resistance, a family history of diabetes, or have been told your blood sugar is high, that's worth discussing with your clinician.

4. Iron (Get Your Ferritin Checked First)

Low iron is very common, especially in women with regular or heavy periods. Symptoms can include:

Fatigue
Hair loss
Anemia
Heart palpitations
Shortness of breath

Ask your clinician to check your ferritin, which reflects your overall iron stores. Ferritin can be low even when you don't have anemia and your other iron labs look normal, which is why I consider it the best screening test for iron deficiency.

Tips for taking iron:

If you can tolerate it, take iron on an empty stomach with vitamin C to improve absorption.
Taking iron every other day may improve absorption and tolerance.
Oral iron can cause an upset stomach, constipation, and darker stools.
Some people can't absorb oral iron and need IV iron infusions. This is common after metabolic and bariatric surgery.

Red flag: If your iron stays low, or you don't respond to supplementation, find out why. Persistently low iron can have serious causes, including colon cancer, especially in people over 40. Always ask, "Why is my iron low?"

I recommend ProCare, a third-party tested brand that offers an iron + vitamin C combination. Use code MetabolicHealth for 10% off. Shop ProCare here. (Affiliate disclosure: I may receive compensation if you purchase through this link.)

For more on this topic, read my related post on fatigue on GLP-1s: https://www.buzzsprout.com/2513787/episodes/19333461

5. Vitamin B12

I don't recommend B12 or B-complex supplements for everyone. If a patient is regularly fatigued, I'll check their B12 level. Most come back normal, but if it's low, an oral supplement can help.

B12 is especially important to monitor if you're vegan or vegetarian, since B12 comes from animal products. In that case, taking a supplement and checking your levels periodically makes sense.

6. Magnesium

Magnesium is popular, but the lab tests we use aren't very accurate and can give false positives or false negatives. Because of that, we sometimes start it empirically.

Possible signs of low magnesium include muscle cramping, fatigue, constipation, and trouble sleeping. If you have these symptoms and your doctor has ruled out other causes, magnesium may be worth trying.

Most people start with roughly 200 to 500 mg per day. Too much can cause loose stools or diarrhea. If that happens, cut back on the dose.

Supplements for Muscle Support on GLP-1s

Protein Supplements

I often recommend protein bars, shakes, and powders for patients on GLP-1s or other obesity medications, and for people after metabolic and bariatric surgery. When you can't tolerate large portions, protein supplements deliver a lot of nutrition in a small package.

They can also:

Work as a meal replacement when your appetite is very low
Help you reach your daily protein goal
Satisfy a sweet tooth, since a protein shake, bar, or dessert can be a goal-friendly way to handle cravings

Creatine

Creatine may support muscle health and growth, but only when paired with resistance or strength training. Without the training, it won't improve muscle function or mass. Together, they can be a useful tool for improving body composition.

There are also interesting early studies on creatine and cognitive function, particularly in perimenopausal and postmenopausal women.

Dose: About 3 to 5 grams per day. More than that can be too much for your body to process.
Caution: If you have heart failure, kidney disease, or liver disease, talk with your doctor first. Creatine can cause water retention, which may be harmful with those conditions.

Collagen

Collagen is often confused with creatine, but it's a type of protein. The strongest evidence is for hair, skin, and nail support and ligament and joint health.

I typically focus first on general protein, then consider creatine. I add collagen only if someone still isn't reaching their goals or has a specific concern with hair, skin, nails, or joints. Not everyone needs collagen.

Gut Health and Hydration Supplements

Fiber

A fiber supplement (psyllium husk, fiber gummies, or capsules) can help if you're struggling to reach your fiber goals through food. Food is the ideal source, but a supplement can be a bridge in the meantime.

Timing: Taking fiber before meals can help fill your stomach and keep portions small. If you're already struggling to eat enough on a GLP-1, try taking it between meals or before bed instead.
Water is essential. Always drink plenty of water with fiber, or it can have the opposite effect and back you up.

Electrolytes

Electrolytes aren't for everyone. They may help if you struggle to drink enough water (your urine should be light yellow or clear) or if you feel lightheaded or dizzy when going from sitting to standing. Check with your doctor to make sure nothing else is going on. A sugar-free electrolyte powder once a day may help boost hydration.

Prebiotics and Probiotics

Talk to your doctor, and ideally a dietitian, before starting these. Nutrition is usually the best route, but for certain conditions, a pre- or probiotic can help, including as a temporary measure while you adjust your eating habits.

Supplements for Insulin Resistance and PCOS

Berberine

Berberine is often compared to metformin. They have similar efficacy and similar side effects. If you have insulin resistance and don't want to take metformin, berberine may be worth considering as an alternative. Talk with your clinician first, especially if you take other medications.

Inositol

Inositol has evidence for people with PMOS (formerly known as PCOS). It can help with insulin resistance as well as the androgenic effects of the condition.

The Bottom Line

Choose third-party tested supplements (USP, NSF, ConsumerLab).
Remember that "natural" doesn't mean safe.
Tell your doctor or pharmacist everything you take.
Skip what you don't need, since more pills means more cost and more interaction risk.
Use labs and symptoms to guide decisions, especially for iron, B12, and magnesium.
Focus on food first, then supplement to fill gaps.

Frequently Asked Questions

Do I need supplements if I'm taking Wegovy or Zepbound?
Not necessarily. If you eat smaller portions, a multivitamin is a reasonable way to cover the basics. Other supplements depend on your labs, symptoms, diet, and health history.

Should I take protein supplements on a GLP-1?
Often, yes. Protein shakes, bars, and powders can help you reach your protein goal when your appetite is low, and they're a helpful tool for protecting muscle during weight loss.

Is berberine a good alternative to metformin?
Berberine has similar efficacy and side effects to metformin, so it may be an option for some people with insulin resistance who don't want to take metformin. Talk with your clinician first.

Is inositol helpful for PCOS?
Inositol has evidence for PCOS/PMOS, including improving insulin resistance and the androgenic effects of the condition.

What's the best test to check for iron deficiency?
Ask for a ferritin level. It reflects your iron stores and can be low even when your other iron labs look normal.

Work With a Missouri Obesity Medicine Physician

If you live in Missouri and want personalized guidance on GLP-1 medications, supplements, PCOS, prediabetes, metabolic syndrome, diabetes, or weight management, I'd love to help. At Missouri Metabolic Health, I treat and prevent metabolic conditions through lifestyle optimization, weight management, and safe, effective medications, all through telehealth.

Learn more and become a patient at Missouri Metabolic Health

Free resources:

Want more? Listen to the full episode of the Modern Metabolic Health podcast, "Supplements on GLP-1s," wherever you get your podcasts.

Medical disclaimer: This content is for educational purposes only and does not constitute medical advice or establish a patient-physician relationship. Always consult your own healthcare provider before starting any new supplement or medication.