The GLP-1 Nutrient Gap: What Your Body Needs on Ozempic, Wegovy, and Mounjaro
GLP-1 medications change how your body absorbs nutrients. Here's what the research says and what you can do about it.
If you’re on semaglutide or tirzepatide, the weight loss part is probably going well. The part nobody talks about is what’s happening to your nutrient levels while the medication does its thing.
GLP-1 medications work by slowing down gastric emptying — food sits in your stomach longer, you feel full faster, you eat less. That’s the whole point. But eating less means absorbing less. And the slower transit through your gut changes which nutrients your body actually picks up along the way.
This isn’t speculation. A 2025 study found that among GLP-1 users, 89.9% fell below recommended intake for magnesium, and over 20% developed a diagnosed nutritional deficiency within their first year on a GLP-1 medication.
[Illustration: How GLP-1 meds affect nutrient absorption]
The big ones to watch
You were probably already low. Most people are. Add reduced food intake from a GLP-1 medication and it gets worse. Magnesium is involved in over 300 processes in your body. Cramps, poor sleep, stress that feels harder to manage — these are all flags.
Magnesium Oxide
~4% absorption
Magnesium Glycinate
High absorption. This is what we carry.
This one is sneaky. Your body stores B12 for months, so deficiency doesn’t show up right away. It’s a slow drain. GLP-1 meds reduce stomach acid production, and B12 needs stomach acid to get absorbed. Fatigue, brain fog, trouble concentrating — sometimes it’s the medication, sometimes it’s B12 quietly dropping.
A study found that semaglutide treatment reduced intestinal iron absorption compared to baseline. If you’re a woman, especially one who menstruates, this is worth monitoring.
You don’t need to take twelve supplements. That defeats the purpose. Start with what matters most for your situation. If you’re cramping and sleeping poorly — magnesium. If you’re foggy and tired — check B12. If your gut is a mess — a probiotic.
[Illustration: Simple supplement bottles]
What you can actually do
Get your levels checked. Ask your doctor for a basic micronutrient panel. It’s simple bloodwork. Most insurance covers it, especially if you mention you’re on a GLP-1.
If you supplement, pay attention to forms. Magnesium glycinate over oxide. Methylcobalamin over cyanocobalamin. The form determines how much your body can actually use.
Don’t trust your multivitamin to cover it. Most multivitamins use cheap forms in small amounts. They’re designed to look good on a label, not to actually move the needle on a deficiency.
Sources
- Frontiers in Nutrition (2025) — Investigating nutrient intake during GLP-1 receptor agonist use
- ScienceDirect (2025) — Nutritional deficiencies and muscle loss in adults with type 2 diabetes using GLP-1 receptor agonists
- PMC (2025) — Nutritional Priorities to Support GLP-1 Therapy for Obesity (Joint Advisory)
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