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Which Magnesium Form Should I Take?
Different magnesium forms have wildly different bioavailability + indication evidence. Glycinate for sleep. Threonate for cognition. Citrate for constipation. Malate for muscle pain. Oxide is the cheap form to avoid. Answer 1-3 questions for a personalized routing.
Quick answer
Bioavailability hierarchy: Glycinate (~80%) > Threonate (~75%) > Citrate (~30%) > Oxide (~4%). Indication matching: Glycinate for sleep + anxiety (glycine carrier is itself calming, Abbasi 2012). Threonate uniquely crosses the blood-brain barrier for cognitive support (Slutsky 2010, Neuron). Citrate is laxative-leaning — best for constipation relief, not daily supplementation. Malate supports muscle pain + fatigue (Russell 1995). Avoid oxide entirely — it's the cheap form in drugstore multivitamins, causing diarrhea before raising serum levels meaningfully. The decision tree below routes you to the right form in 1-3 questions.
Magnesium Form Decision Tree
Answer 1-3 questions to find the right magnesium form for your specific use case. Different forms (glycinate, threonate, citrate, malate, oxide) have wildly different bioavailability + side-effect profiles. Anchored to: Abbasi 2012, Slutsky 2010 Neuron, Russell 1995, Saris 2000 (absorption review).
Why magnesium form matters so much
Magnesium needs a carrier molecule to absorb across the gut wall. The choice of carrier changes everything: how much actually enters the bloodstream, what side effects you get, whether it reaches the brain, whether it supports the specific outcome you're after. Treating "magnesium" as a single thing is one of the most common supplement mistakes.
The form that's in your drugstore multivitamin is almost certainly magnesium oxide — ~4% bioavailable, the cheapest to manufacture, and the form that causes diarrhea before it does anything useful. Saris et al. 2000 (Magnesium Research) reviewed magnesium-form absorption studies and ranked oxide as the worst-performer across all measured endpoints. If your supplement label just says "Magnesium" without specifying the form — it's probably oxide.
Glycinate (chelated to glycine) is the universal default because: (a) ~80% bioavailable, (b) glycine itself is a mild calming neurotransmitter making it synergistic with sleep + anxiety indications, (c) minimal GI side effects mean you can dose up without diarrhea, (d) it works as a general-purpose magnesium for users without a specific indication.
For deeper-than-decision-tree-level breakdown of each form, see our magnesium glycinate vs threonate vs citrate guide and magnesium glycinate glossary entry.
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