If you've stood in the supplement aisle staring at three bottles that all say "magnesium," you're not alone. The word on the label is the same, but the form attached to it changes how well your body absorbs it, how it affects your stomach, and whether it's a good fit for sleep.
The one difference that matters: bioavailability
Bioavailability is how much of the magnesium your body can actually absorb. Magnesium oxide is roughly 4% absorbed, citrate around 12–16%, and glycinate the highest at about 20–25%. If your goal is to raise your magnesium levels for rest and relaxation, absorption is the number to watch.
Why glycinate is the go-to for sleep
Magnesium glycinate binds magnesium to glycine, an amino acid that acts as a calming neurotransmitter precursor. You get better-absorbed magnesium plus a compound associated with relaxation. Many people also find glycinate is gentle on the stomach, so it doesn't cause the digestive upset that higher-dose oxide and citrate can.
When citrate or oxide makes more sense
Citrate absorbs well and has a mild laxative effect, so it can help if you deal with occasional constipation alongside restless nights. Oxide is poorly absorbed and is generally used short-term for bowel regularity, not for topping up your magnesium for sleep.
The bottom line
For sleep and relaxation with a gentle stomach, magnesium glycinate is usually the best-matched form. Our Magnesium Glycinate — Calm & Sleep uses the glycinate form for exactly these reasons: high absorption, calming glycine, gentle on digestion, third-party tested and cGMP-manufactured.
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This article is for general information only and isn't medical advice. Talk to a healthcare professional before starting any supplement.