Yes, you can take magnesium and vitamin B12 together, even at the same time. We found no documented absorption conflict and no study of the pair, so timing is a matter of habit. Two points matter more. The NIH Office of Dietary Supplements says B12 supplementation does not appear to improve athletic performance or endurance in people with sufficient B12 status, and we found no evidence that it lifts everyday energy in them either. The real overlap is medication: proton pump inhibitors can affect magnesium status, and gastric acid inhibitors and metformin may affect B12 levels, so anyone on a long-term acid reducer or metformin should ask a doctor about checking levels rather than guess. The adult upper limit for magnesium from supplements and medicines is 350 mg a day; B12 has none.
This content is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or qualified healthcare provider before starting any supplement regimen.
Pair checker
Can I take these together?
Yes. NIH sources document no interaction between magnesium and vitamin B12, so they can share a dose.
Why
Neither NIH fact sheet lists the other nutrient as an interaction. They overlap on medicines instead: proton pump inhibitors can affect magnesium status, and acid reducers and metformin may lower B12 levels.
Timing
Take them together, at whatever time you will remember. If you take a long-term acid reducer or metformin, ask your doctor whether your levels should be checked.
Sources
Check your whole list, not just one pair
Supplement Tracker checks every supplement you take against the others and reminds you of each dose at its own time.
By three o'clock most afternoons you are reading the same email twice, so when a wellness newsletter recommended an "energy stack" of vitamin B12 in the morning and magnesium glycinate at night, you ordered both. The bottles now stand next to the kettle. Before they turn into a routine, one practical question: can you take magnesium and B12 together, or does each need its own time of day?
You can take them together, in the same handful if that is easiest. We found no study that tested magnesium and B12 as a pair and no documented absorption conflict between them, so nothing calls for spacing them apart. Two other points matter more than the timing. If your B12 is already fine, we found no evidence that more of it will give you more energy. And the real overlap between these two is a shared risk factor: long-term acid-reducing medicine may affect both, which is a reason to have your levels checked rather than to guess.
Do Magnesium and Vitamin B12 Interfere?
Not that we could find. The magnesium fact sheet from the NIH Office of Dietary Supplements (ODS) says magnesium "may interact with certain medications, such as oral bisphosphonates, tetracyclines, and quinolone antibiotics." The ODS vitamin B12 fact sheet has its own list of medicines to watch. We found no warning about the other nutrient on either sheet, so sharing a slot is simply convenient. The two lists do meet at one point, acid-reducing medicine, which gets its own section below.
Why People Pair Them
The usual pitch is energy: B12 to lift the afternoon, magnesium to settle the evening. The evidence for that pitch is thin.
Vitamin B12. The body needs micrograms: ODS puts the recommended intake at 2.4 to 2.8 mcg a day for adults. On performance, the fact sheet is plain: "Vitamin B12 supplementation does not appear to improve athletic performance or endurance in people who have sufficient vitamin B12 status." That sentence is about sport, and we found no better evidence for B12 energy claims in everyday life. If your B12 is already fine, a supplement is not a proven pick-me-up.
The case for taking it rests on being low, or at risk of becoming low. ODS names the groups at higher risk of deficiency: older adults, people with pernicious anemia or gastrointestinal disorders, people who have had gastrointestinal surgery, vegetarians, and infants of vegan mothers. Our guide to who actually needs vitamin B12 goes through those groups.
Magnesium. ODS describes magnesium as playing "a role in the active transport of calcium and potassium ions across cell membranes, a process that is important to nerve impulse conduction, muscle contraction, and normal heart rhythm." We found no trial that tested magnesium and B12 together for tiredness, so the energy stack is an untested idea. If fatigue put both bottles on your counter, our guide to supplements for energy covers what is worth checking first, and our page on magnesium deficiency symptoms covers the magnesium side.
The Real Overlap: Proton Pump Inhibitors
On the magnesium side, ODS says that "some medications, including diuretics and proton pump inhibitors, can affect magnesium status." On the B12 side: "some medications, including gastric acid inhibitors and metformin, may affect vitamin B12 levels." Proton pump inhibitors are a kind of gastric acid inhibitor, so they turn up on both sheets. The B12 sheet also notes that B12 in food is bound to protein, and that stomach acid and protease, a protein-digesting enzyme, release it before it can be absorbed.
Low magnesium is not always trivial: in severe cases, ODS notes, magnesium deficiency "can cause hypocalcemia or hypokalemia," meaning low blood calcium or low blood potassium.
If you have taken a proton pump inhibitor for a long time, ask your doctor whether your magnesium and B12 levels should be checked; if you are not sure whether your acid reducer is one, your pharmacist can tell you. If you take metformin, ask about B12; if you take a diuretic, ask about magnesium. If a level comes back low, your doctor can say what to take and how much, a step that buying both bottles on a hunch skips. Keep taking the medicine as prescribed while you ask.
Practical Recommendations
This is our suggested routine, not a tested protocol.
- Take them together if that is easiest. One slot, one glass of water.
- Let habit choose the hour. We found no evidence that either works better at a particular time of day, so pick the slot you are least likely to forget. If you want magnesium at bedtime, or a larger dose sits badly with you, our guide to the best time to take magnesium covers morning, night and split doses. B12 can go wherever the magnesium goes.
- Read the labels you already own. A B-complex or multivitamin may already contain B12, magnesium or both. Check before adding another bottle, and count any magnesium toward the limit below. If your B12 comes with folic acid, our B12 and folate page explains how those two interact.
- Check the timing with certain prescriptions. Oral bisphosphonates, tetracyclines and quinolone antibiotics may interact with magnesium. Ask your pharmacist how to time magnesium around them, or follow the drug's label.
Dosage Considerations
Magnesium: "The Tolerable Upper Intake Level for supplemental magnesium is 350 mg for adults," per the ODS magnesium sheet, and 65 to 350 mg for children and teenagers, depending on age. The limit counts magnesium from supplements and medicines, not from food. The recommended intake for adults, 310 to 420 mg a day, covers everything you take in, food included, which is why the two numbers can look out of step. The sheet also warns that "high doses of magnesium from dietary supplements or medications can cause diarrhea, nausea, and abdominal cramping."
Vitamin B12: the recommended intake is 2.4 to 2.8 mcg for adults, and there is no upper limit: "Vitamin B12 does not have a tolerable upper intake level because it is generally considered to be safe, even at high doses." Of the two, magnesium is the one with a ceiling.
Who should check first:
- People with kidney disease. The kidneys regulate magnesium, so ask your doctor before taking it as a supplement.
- Anyone on a long-term acid reducer, metformin or a diuretic. The overlap section above covers which levels to ask about.
- Anyone on oral bisphosphonates, tetracyclines or quinolone antibiotics. Ask your pharmacist how to time magnesium around them.
- Older adults and the other B12 risk groups above. Ask whether a B12 test makes sense before relying on a supplement.
Key Takeaway
You can take B12 and magnesium together, at the same time if that suits you: we found no conflict between them and no study of them as a pair. If your B12 is already fine, we found no evidence that more of it gives you more energy. The overlap worth acting on is medication: long-term acid reducers appear on both ODS sheets and metformin on the B12 one, so if either applies to you, ask your doctor about checking your levels instead of guessing. Keep supplemental magnesium, medicines included, within the 350 mg adult limit unless your doctor says otherwise.
Track Your Timing
Supplement Tracker lets you put magnesium and B12 in the same time-of-day slot, or in separate ones, each slot with its own reminder time, and check off every dose as you take it. When you ask your doctor about checking your levels, the dated history shows what you have taken and since when.
