Appetite medications like Ozempic, Wegovy, and Mounjaro have changed how millions of people eat. Portions shrink, cravings go quiet, and a few bites can feel like a full meal. That shift is the point of the medication, but it raises a question many people never think to ask: when you eat far less food, where do your vitamins and minerals come from? GLP-1 nutrient deficiencies are a fast-growing area of research, and the early findings are clear enough to act on.

When you’re eating less, every bite has to carry more nutritional weight. Your genes also shape how well you absorb and use certain nutrients, so two people on the same prescription can face very different gaps.

Below, we cover what researchers are seeing, which genes matter most, and where DNA-powered nutrition fits.

What Are GLP-1 Nutrient Deficiencies?

GLP-1 nutrient deficiencies are shortfalls in vitamins and minerals that can develop when appetite-suppressing GLP-1 receptor agonists reduce how much a person eats. Less food means fewer chances to take in micronutrients, and slower digestion may also change how some are absorbed.

A February 2026 narrative review in Clinical Obesity pulled together six studies covering more than 480,000 adults using these medications for diabetes, obesity, or both. Vitamin D deficiency was the most common issue. In the largest study, 13.6% of users had developed it by 12 months. Iron deficiency, anemia, and B vitamin deficiencies also appeared over the same period, though less often. The authors suggested clinicians treat nutritional shortfalls as a common consequence of therapy and monitor for them.

Which Nutrients Fall Short Most Often?

Vitamin D, calcium, and iron top the list, with B vitamins close behind. A 2025 cross-sectional study in Frontiers in Nutrition analyzed food records from 69 adults taking GLP-1 medications. Only 1.4% met the full recommended intake for vitamin D. Most fell short on calcium, and roughly two-thirds took in less iron than the average requirement. Fiber, magnesium, potassium, and choline were often low as well.

None of this means the medication is the problem. It means a lighter plate leaves less room for error. A few patterns make gaps more likely:

• Skipped meals. When hunger disappears, it’s easy to go hours without eating anything.
• Less protein. Meat, fish, eggs, and dairy supply iron, B12, and vitamin D, and they’re often the first foods pushed aside when you feel full.
• Fewer fortified foods. Cutting back on cereal, milk, and bread can mean less added vitamin D, calcium, and folic acid.
• Digestive side effects. Nausea can narrow what people are willing to eat.

How Your Genes Shape GLP-1 Nutrient Deficiencies

Eating less affects everyone. Your genes help decide which shortfalls show up first and how hard they hit.

VDR: How Well You Respond to Vitamin D

The VDR gene builds the vitamin D receptor, which lets your cells respond to vitamin D. SNiP tests four common VDR variants: Fok1, Bsm1, Apa1, and Taq1. People who carry several of them may need more vitamin D support to get the same effect, and that need grows when diet supplies very little. Our guide to vitamin D and your genes explains each variant.

FUT2: Absorbing Vitamin B12

FUT2 rs602662 is a marker tied to vitamin B12 absorption. A genome-wide study in Nature Genetics linked common FUT2 variants to differences in blood B12 levels. If your result points to lower absorption and you’re also eating less meat, fish, and dairy, B12 deserves attention. Learn more in Vitamin B12: Optimizing Genetic Expression and Ensuring Safety.

MTHFR and MTRR: Using Folate and B12

Absorption is only half the work. MTHFR (C677T and A1298C) affects how efficiently you convert folate into its active form, and MTRR helps recycle B12 so it can keep supporting methylation. Variants in either gene can raise your need for the active forms of these nutrients. We explain why in B12 and Folate for Women.

FTO: Appetite and Weight

FTO is one of the best-studied genes linked to appetite, fat mass, and weight. Many people who start GLP-1 medications have spent years fighting what felt like a louder hunger signal. Your FTO results add context to that history and can inform how you support your metabolism over the long run.

How to Make Every Bite Count

When your appetite is smaller, food quality matters more. Which nutrients your smaller plate most needs to carry depends on your genes, so your SNiP results come first and these habits build on them:

• Lead with protein at each meal, then add vegetables and whole grains.
• Choose nutrient-dense foods like eggs, salmon, sardines, Greek yogurt, lentils, leafy greens, and fortified milk.
• Eat on a schedule, even when hunger doesn’t prompt you. Three small meals beat one rushed one.
• Pair iron-rich foods with vitamin C, such as beans with peppers or spinach with citrus.
• Get safe sun exposure when the season allows.

If you’ve wondered about natural options people compare with these drugs, our article on berberine, the supplement dubbed “nature’s Ozempic” separates the social media buzz from the science.

One important line: every decision about your medication, including dose changes, belongs with your prescriber. Tell your care team about each supplement you take.

Where DNA-Powered Nutrition Fits

Your genes show where a lighter diet is most likely to leave you short, and a daily formula built around them is the foundation your food choices build on, because it matches the body you actually have.

Your CODE Complex^® formula is built around your results for key genes, including several that matter on a reduced-calorie plan:

• VDR: vitamin D3, vitamin K2, and calcium, dosed on your results for all four VDR markers
• FUT2: methylcobalamin, Quatrefolic®, and SAMe, matched to your B12 absorption marker
• MTHFR: Quatrefolic®, choline, and TMG
• MTRR: methylcobalamin, P5P, riboflavin 5’-phosphate, zinc, and other cofactors
• FTO: alpha lipoic acid, bamboo leaf, dihydroberberine, and vitamin C

Every formula also includes a Base blend with digestive enzymes. Your genes don’t change, so these results stay relevant for life, during treatment and long after it. As with any supplement, share your formula with your prescriber, especially if you take a GLP-1 or another medication that affects blood sugar, so your whole plan works together.

Common Questions About GLP-1 Nutrient Deficiencies

Do GLP-1 medications cause nutrient deficiencies?
They can contribute to them. People using these medications often eat much less, and a 2026 review found vitamin D, iron, and B vitamin deficiencies among users. Diet quality and genetics influence individual risk.

What vitamins should I focus on while taking a GLP-1?
Vitamin D, calcium, iron, and B12 come up most often in research. Your prescriber can help you watch these, and your DNA results show which ones your body is most likely to need extra support with.

Can my genes affect how I absorb nutrients on a GLP-1?
Yes. FUT2 influences B12 absorption, and VDR affects how your cells respond to vitamin D. These differences matter more when food intake drops.

Should I stop my medication if I’m worried about deficiencies?
No. Never change or stop a prescription on your own. Talk with your prescriber, who can help you address nutrition alongside treatment.

The Takeaway

Eating less doesn’t have to mean getting less. When appetite shrinks, nutrition has to work smarter, and your DNA shows where your body needs the most support.

Ready to make every bite count? Get started with SNiP. Already have DNA data from 23andMe or AncestryDNA? Enter your results to receive your personalized CODE Complex^® formula.

SNiP Nutrigenomics — Precision nutrition, powered by your DNA.