Does Ozempic deplete B12? What we know

There is no good evidence that Ozempic (semaglutide) depletes vitamin B12. Unlike metformin, which is well documented to lower B12 over years of use, GLP-1 medicines have not been shown to interfere with B12 absorption. The more likely issue is intake: when you eat far less food, you take in less B12 along with everything else.

That said, plenty of people on semaglutide also take metformin, and many have been eating small portions for months. Both of those are worth a conversation with your doctor, and a blood test settles it far better than a guess.

Does semaglutide affect B12 absorption?

B12 absorption is a fussy little relay. Stomach acid frees B12 from protein, intrinsic factor made in the stomach lining picks it up, and the pair is absorbed near the end of the small intestine. A drug can interfere at any of those steps. Metformin appears to interfere at the last one, and long-term users show lower B12 in studies including the Diabetes Prevention Program Outcomes Study, published in the Journal of Clinical Endocrinology and Metabolism in 2016.

Semaglutide works differently. It slows gastric emptying and reduces appetite. Slower emptying changes the timing of digestion, not the machinery of B12 uptake, and the semaglutide trial programme has not reported B12 deficiency as a signal. So the honest summary is: no established depletion mechanism, and a real intake question.

How much B12 do you actually need?

The NIH Office of Dietary Supplements puts the adult RDA at 2.4 mcg a day, rising a little in pregnancy and breastfeeding. That is a small number, and a single serving of beef, salmon, eggs or dairy clears it. The catch is that "a serving" assumes you finished it.

Nutrient	Typical daily amount	Why it matters	What research looked at
Vitamin B12	2.4 mcg RDA (supplements often give far more)	Nerve function, red blood cells, energy metabolism	NIH ODS fact sheet; long-term metformin and B12 status in DPPOS, JCEM 2016
Folate	400 mcg DFE	Works alongside B12; high folate can mask a B12 shortfall on a blood count	NIH ODS; folic acid fortification research
Vitamin B6	1.3 to 1.7 mg for adults	Amino acid and neurotransmitter metabolism	NIH ODS fact sheet
Iron	8 mg for men, 18 mg for premenopausal women	Oxygen transport; low intake shows up early when portions shrink	NIH ODS; trials of ferrous bisglycinate tolerability
Protein	Roughly 0.8 g per kg as a floor, often more when losing weight	Preserves lean mass during weight loss	Nutrition and obesity literature on lean mass during caloric restriction

If your portions have halved, so has your dietary B12, along with the iron and the protein sitting on the same plate. We wrote about that pattern in Eating less on a GLP-1? The nutrient gaps that show up first.

What are the signs of low B12 to watch for?

Low B12 is quiet before it is loud. Fatigue, breathlessness on stairs, a sore or smooth tongue, pins and needles in the hands or feet, and trouble concentrating are the common ones. Nerve symptoms matter most because they can persist if a deficiency runs long, so tingling or numbness is a call-your-doctor symptom rather than a wait-and-see one.

Be careful about self-diagnosing here. Fatigue on a GLP-1 has a long list of possible causes, starting with eating less overall. A serum B12 test, sometimes with methylmalonic acid if the result is borderline, is what actually answers the question.

Should you take a B12 supplement on Ozempic?

Ask your prescriber, especially if you also take metformin or a proton pump inhibitor, both of which have better-supported links to lower B12. If you are vegan or vegetarian, you were already in the group that the NIH ODS flags as at risk, and eating less makes that gap wider.

For most people a modest oral dose covers ordinary dietary shortfall. Absorption through intrinsic factor saturates at a small amount per dose, which is why supplement labels carry numbers that look absurd next to a 2.4 mcg RDA: a small percentage of a large oral dose gets through by passive diffusion. That is a design decision, not a typo, and it is the kind of thing worth understanding when you are reading a supplement label.

Methylcobalamin or cyanocobalamin?

Both raise B12 levels. Cyanocobalamin is cheaper, extremely stable, and is what most of the long-running research used. Methylcobalamin is one of the forms your body uses directly, and some people prefer it for that reason. The evidence that one clearly beats the other for a healthy adult topping up a dietary gap is thinner than the internet suggests. We go through the case for the active forms in Methylated B12, folate and B6.

Keel is the thing we happen to make for this: digestive enzymes, probiotics, ginger and peppermint alongside methylated B12, folate, B6, iron, zinc, magnesium, biotin, D3 and BioPerine, two capsules a day.

What about the nausea and the slow stomach?

Slowed gastric emptying is doing a lot of the work on a GLP-1, and it is also behind the fullness, the early satiety and the queasy afternoons. That is a food-timing problem more than a supplement problem: smaller meals, protein first, and going gently on very fatty food. Ginger and peppermint are the traditional standbys when appetite does something new, and we looked at what the studies actually measured in Ginger + peppermint when your appetite does something new.

If you are taking iron too, take it with food and pick a gentle form, because an already slow stomach does not need the argument. More on that in Iron, the right kind of gentle.

The wider picture is in our guide to eating and supplementing well on GLP-1 medications.

FAQ

Does Ozempic cause B12 deficiency? No study has shown that semaglutide depletes B12. Reduced food intake can lower how much B12 you eat, and metformin taken alongside it has a much better-documented link to low B12.

How much B12 should I take on a GLP-1? Ask your doctor, since the right answer depends on your blood level and your other medicines. The adult RDA is 2.4 mcg a day per the NIH Office of Dietary Supplements; oral supplements commonly supply much more because only a fraction of a large dose is absorbed.

Can I get my B12 tested? Yes, a serum B12 test is routine, and your doctor may add methylmalonic acid or homocysteine if the result sits in the grey zone. Test before you supplement heavily, because supplementing first can make the result harder to read.

Is B12 deficiency reversible? Blood markers usually respond well to treatment under medical supervision. Nerve symptoms are the reason not to wait: the longer they run untreated, the less certain the recovery, so raise them with your doctor early.

Do I need injections instead of capsules? Some people do, particularly with pernicious anaemia or after certain bowel surgeries, where the absorption relay is genuinely broken. That is a prescriber's call, not a shelf decision.

Sources

• Aroda et al., Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study, JCEM
• NIH Office of Dietary Supplements, Vitamin B12 fact sheet

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.