The Best Supplements for GLP-1 Users: What the Evidence Actually Shows

GLP-1 receptor agonists like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) have reshaped how we think about weight management. For people who have struggled with hunger-driven eating for years, the appetite suppression these medications provide can feel like a fundamental shift.

But appetite suppression creates a problem that doesn’t get enough attention: when you eat significantly less food, you get significantly fewer nutrients, including the ones your body needs to preserve muscle during weight loss.

This guide covers the supplements with the clearest evidence for addressing GLP-1-specific nutritional concerns, based on what researchers and clinicians following these patients closely are finding.

How we evaluate products in this guide

These recommendations are based on whether the ingredient and dose matches what clinical research supports for the specific concern, whether the product has meaningful third-party certification, and whether the formulation quality is appropriate for daily use. We do not conduct hands-on product testing.

Understanding the gaps GLP-1 medications create

When you’re eating 1,000 calories per day instead of 2,000, you’re not just eating less. You’re potentially missing half of your daily protein target, half of your vitamin and mineral intake, and dropping well below recommendations for calcium, B12, iron, and fiber. The muscle loss data is the most acute concern.

A 2024 paper in Obesity Reviews noted that lean mass loss on GLP-1 medications in clinical trials represents a higher proportion of total weight lost than is typically seen with diet-alone interventions, with some analyses placing lean mass loss at 25–40% of total weight lost. Protein and resistance training are the primary tools to counter this.

Priority 1: Protein

Protein is the most important nutritional concern for GLP-1 users. The research consistently supports higher protein intake during weight loss to preserve lean mass. The widely cited target for people actively trying to preserve muscle during weight loss is 1.2–1.6 grams of protein per kilogram of body weight, higher for older adults and those doing resistance training.

At 1,000–1,200 calories per day, hitting this target through food alone is extremely difficult. Protein supplementation isn’t optional in this context; it’s part of the nutritional strategy.

What to look for: Complete protein from high-quality sources (whey, casein, pea, soy). At least 20–25 grams of protein per serving. NSF or Informed Sport certification, which confirms the product contains what the label says and is tested for banned substances.

Formulation note: Whey isolate is digested quickly, making it useful post-workout. Casein digests more slowly and is better for a meal replacement or before-bed protein. Pea protein is a practical plant-based option with a solid amino acid profile.

Products worth looking at: Transparent Labs 100% Whey Protein Isolate (NSF Certified for Sport) and Garden of Life Sport Organic Protein (NSF Certified for Sport) both have verifiable third-party certification and minimal unnecessary additives. For plant-based options, Orgain Organic Protein has good macros and is widely available.

Priority 2: Creatine monohydrate

Creatine has become a mainstream recommendation in clinical discussions about GLP-1 medications because of the muscle loss risk. It’s not just for athletes. Creatine supports ATP regeneration (the primary energy currency in muscle cells), and consistent supplementation has been shown to improve muscle retention during calorie restriction across multiple randomized trials.

A 2021 review in Nutrients found that creatine supplementation during resistance training produced significantly greater lean mass preservation than resistance training alone. For GLP-1 users, where caloric intake is severely limited and protein synthesis is already challenged, creatine provides meaningful additional support.

Dose: 3–5 grams of creatine monohydrate daily. No loading phase needed.

Products worth looking at: Thorne Creatine is NSF Certified for Sport and contains only creatine monohydrate. Klean Athlete Klean Creatine is similarly certified. Both contain no artificial flavors, fillers, or unnecessary ingredients.

Priority 3: Vitamin D

Vitamin D deficiency is extremely common at baseline, with some surveys suggesting over 40% of adults in the US have insufficient levels. On a severely calorie-restricted diet with reduced intake of vitamin D-containing foods (fatty fish, egg yolks, fortified dairy), the risk of deficiency compounds.

Vitamin D3 (cholecalciferol) is the form that most efficiently raises blood levels of 25-hydroxyvitamin D, the marker measured on standard blood tests. The NIH Office of Dietary Supplements notes that blood levels below 30 nmol/L are considered deficient, and levels between 30–50 nmol/L may be inadequate for bone health in some people.

Dose: 1,000–2,000 IU of vitamin D3 daily is a reasonable maintenance dose for most adults. Getting your levels tested before starting is worthwhile.

Formulation note: Taking vitamin D3 with vitamin K2 (specifically MK-7 form) has mechanistic support since vitamin K2 helps direct calcium to bones rather than arteries. Several combination D3/K2 products are available from well-regarded brands.

Priority 4: A quality multivitamin

On 1,000–1,200 calories per day of whatever foods you can tolerate, it’s difficult to hit micronutrient targets consistently. A comprehensive multivitamin doesn’t cover every gap (it’s not a substitute for protein or creatine), but it addresses the broad spectrum of vitamins and minerals that become harder to meet at very low intakes.

What to look for: Folate as methylfolate rather than folic acid (better utilized by people with MTHFR variants), B12 as methylcobalamin, chelated mineral forms, no megadoses of fat-soluble vitamins (A, D, E, K), which can accumulate.

Products worth looking at: Thorne Basic Nutrients 2/Day and Pure Encapsulations O.N.E. Multivitamin both use more bioavailable forms of B vitamins and minerals, are manufactured under rigorous quality controls, and avoid the synthetic dyes and fillers found in many mass-market multivitamins.

Priority 5: Fiber supplementation

GLP-1 medications significantly slow gastric emptying, which combined with low food intake, commonly causes constipation. Most people eating 1,000–1,200 calories of whatever their appetite allows are well below the 25–38 grams of fiber per day recommended for adults.

Psyllium husk (the active ingredient in Metamucil) is the most evidence-based fiber supplement available. It’s been shown in randomized trials to improve constipation, reduce the severity of IBS symptoms, and modestly lower cholesterol. A heaping teaspoon in water once or twice daily adds 3–6 grams of soluble fiber without adding significant calories.

Priority 6: Probiotic (for GI side effects)

Nausea, bloating, and constipation are the most commonly reported side effects of GLP-1 medications, particularly in the first weeks of use or after dose increases. Probiotics don’t directly address the cause (slowed gastric emptying), but Lactobacillus rhamnosus GG and Saccharomyces boulardii have evidence for reducing GI discomfort and regulating bowel habits during periods of dietary disruption.

This is a lower-priority addition compared to protein and creatine, but relevant if GI symptoms are significantly affecting quality of life or adherence to the medication.

What not to bother with

“GLP-1 support” proprietary blends: A growing number of products have appeared marketing themselves specifically for GLP-1 users. Most contain berberine, berbamine, or other compounds with general metabolic claims but no specific evidence for addressing GLP-1-induced nutritional gaps. The marketing is newer than the evidence.

High-dose fat-soluble vitamins: At 1,000–1,200 calories per day with reduced fat intake, fat-soluble vitamin absorption (A, D, E, K) may actually be lower than usual. However, high-dose supplementation of fat-soluble vitamins can cause toxicity at sustained intakes. Stick to standard multivitamin doses.

The bottom line

GLP-1 medications are effective for weight loss but create a nutritional environment that requires active management. The priority list is: adequate protein (supplemented when food intake can’t cover it), creatine to preserve lean mass, vitamin D, and a comprehensive multivitamin. Fiber and probiotics are practical additions for managing the GI side effects most users experience.

If you have a prescribing physician, ask for a referral to a registered dietitian with bariatric or weight management experience. The nutritional strategy during GLP-1 therapy matters as much as the medication itself for long-term body composition outcomes.