Which Type of Magnesium Should You Take? Glycinate vs Citrate vs Threonate After 40
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“Magnesium” isn’t one thing — the form it’s bound to changes how well it absorbs, how it affects your digestion, and what it’s actually good for. If you searched for the best magnesium and got overwhelmed by glycinate, citrate, and threonate, here’s the practical difference.
Quick comparison
| Form | Best known for | GI effect | Typical cost |
|---|---|---|---|
| Glycinate (bisglycinate) | Sleep, general relaxation, well-tolerated daily use | Gentle, low laxative effect | Moderate to higher |
| Citrate | Occasional constipation, muscle cramps | Noticeable laxative effect at higher doses | Lower |
| L-Threonate | Cognitive function/brain health research, marketed for sleep | Gentle | Highest (patented form, lower elemental magnesium per dose) |
Glycinate: the well-rounded daily pick
Magnesium bisglycinate is magnesium bound to the amino acid glycine, which makes it well-absorbed and easy on most people’s stomachs compared to cheaper forms like magnesium oxide. It’s the form most commonly recommended for general daily use, sleep quality, and muscle relaxation, and it’s the form we’ve reviewed directly — see our Thorne Magnesium Bisglycinate review (NSF Certified for Sport) and our Thorne vs Doctor’s Best comparison for a lower-cost non-certified alternative in the same form.
Citrate: budget-friendly, but check the GI effect
Magnesium citrate is well-absorbed and typically cheaper than glycinate, but it has a more noticeable laxative effect — which is exactly why it’s the form most often used for occasional constipation. If your main goal is muscle cramps or general supplementation and you don’t want a digestive effect, glycinate is usually the more comfortable daily choice; citrate makes sense if gentle regularity support is actually part of what you’re looking for.
L-Threonate: the “brain” form, at a price
Magnesium L-threonate (often sold under the patented name Magtein) is the form studied specifically for crossing into brain tissue, and it’s marketed heavily for cognitive function and sleep. It typically delivers less elemental magnesium per dose than glycinate or citrate, and costs noticeably more per serving. The research is promising but earlier-stage than the decades of data behind glycinate and citrate — reasonable to try if cognitive/sleep support is your specific goal and budget isn’t the deciding factor, but not a form we’d recommend as a first magnesium supplement.
Which should you pick?
- General daily use, sleep, muscle relaxation, sensitive stomach → glycinate
- Occasional constipation or you don’t mind a mild laxative effect → citrate
- Specifically chasing cognitive/brain-health benefits and budget isn’t the concern → L-threonate
Not sure you need magnesium at all yet? Start with our Magnesium for Active Adults Over 40 guide.
Sources
- General supplement-form comparisons from manufacturer and third-party ingredient information; individual response to any magnesium form varies by person.
- This is educational content, not medical advice — talk to a doctor before starting a new supplement, especially alongside other medications.