Magnesium Forms Explained: Glycinate vs Citrate vs Threonate vs Oxide

The magnesium itself is identical across all forms. What changes is what it's bonded to, and that bond determines how well your body absorbs it. Think of it like this: the magnesium is the passenger, the bonded compound is the vehicle. Some vehicles get through customs easily. Others get stuck at the border.

Magnesium oxide? Cheap vehicle. About 4% of it makes it into your bloodstream. The rest passes through your digestive tract (which is why it works as a laxative, but not much else).

Magnesium glycinate? Premium vehicle. Around 80% bioavailability. Your body recognizes the amino acid glycine and absorbs the whole package efficiently.

This matters for your wallet too. If you buy oxide because it's cheaper per pill, you're actually paying MORE per milligram of absorbed magnesium.

Magnesium glycinate has ~80% bioavailability and is the top choice for sleep quality, anxiety, and general supplementation. It's bonded to glycine, an amino acid that itself has calming properties. Double benefit.

12 randomized controlled trials support magnesium for sleep improvement. The glycinate form specifically is gentle on the stomach (unlike citrate) and doesn't cause the laxative effect that oxide does.

Dose: 300-400mg elemental magnesium, 30-60 minutes before bed.
Cost: $15-25/month for quality brands.
Who it's for: Most people. If you're only going to take one form, this is it.

One thing to watch: check the label for "elemental magnesium." A capsule might contain 1,000mg of magnesium glycinate compound but only 200mg of actual magnesium. The elemental amount is what matters.

Magnesium citrate offers ~25% bioavailability with good general absorption and a mild laxative effect that some people find helpful. It's the most common form in supplements and one of the better-studied.

If constipation is part of your picture, citrate does double duty. The citric acid component draws water into the intestines. Not aggressively (that's oxide territory), but noticeably.

Dose: 200-400mg elemental magnesium.
Cost: $10-20/month. One of the cheapest quality forms.
Who it's for: People who want general magnesium supplementation and don't mind (or actively want) the mild digestive effect.

Downside: some people get loose stools even at moderate doses. If that's you, switch to glycinate.

Magnesium L-threonate (Magtein) is the only form shown to cross the blood-brain barrier effectively, making it the top choice for cognitive function and memory. A 2010 MIT study demonstrated it increased brain magnesium levels by 15% while other forms didn't meaningfully affect brain concentrations.

Dose: Typically 1,500-2,000mg of magnesium threonate compound (which delivers ~140mg elemental magnesium). Yes, the elemental dose is lower. The value is in WHERE it goes.
Cost: $30-50/month. The most expensive common form.
Who it's for: Cognitive focus, age-related memory concerns, brain health optimization.

The downside: cost, and the elemental magnesium per dose is low. If you need both brain benefits AND general magnesium, you might combine threonate (morning) with glycinate (evening). That's what many biohackers do.

Magnesium oxide has only ~4% bioavailability, making it one of the worst forms for supplementation despite being the cheapest and most common. This is the form in most multivitamins and cheap standalone supplements. And it's the form in most "400mg magnesium" products that cost $8.

Do the math: 400mg x 4% absorption = 16mg of usable magnesium. You'd need to take 25 pills to match what one glycinate capsule delivers.

The ONE legitimate use: as a laxative. Milk of Magnesia is magnesium oxide/hydroxide. For that purpose, the low absorption IS the feature.

If your current supplement uses oxide as the primary form, you're probably not getting meaningful magnesium. Check the label.

Here's the honest comparison. Pick the form that matches your primary goal.

Magnesium Glycinate (80% absorption)
Best for: Sleep, anxiety, general use. Gentle. Our #1 recommendation.

Magnesium Citrate (25% absorption)
Best for: General use + constipation relief. Good value.

Magnesium L-Threonate (60% absorption)
Best for: Brain health, memory, cognitive function. Premium price.

Magnesium Malate (35% absorption)
Best for: Energy production, fibromyalgia, muscle pain.

Magnesium Taurate (40% absorption)
Best for: Heart health, blood pressure. Taurine adds cardiac benefits.

Magnesium Oxide (4% absorption)
Best for: Nothing (except laxative effect). Avoid for supplementation.

Want to check if your magnesium supplement uses the right form? Our ingredient pages show the bioavailability data for every form.