Magnesium is one of the most supplemented minerals — and one of the most confusing to shop for. There are over a dozen commercially available forms, each with different absorption rates, target effects, and tolerability profiles. Choosing the wrong form means you’re either underdosing, overspending, or getting an effect you didn’t want.
Magnesium Glycinate
Magnesium bound to glycine, an amino acid. High bioavailability (~80% absorption), gentle on the stomach, and the glycine itself has calming properties. This is the go-to form for general supplementation, stress support, and sleep. The downside: it’s bulkier per milligram of elemental magnesium, so capsules are larger or you need more of them.
Typical dose: 200–400mg elemental magnesium before bed. Glycinate is unlikely to cause the GI distress associated with cheaper forms.
Magnesium Threonate (Magtein)
The only form clinically shown to cross the blood-brain barrier and increase brain magnesium levels. Developed at MIT, patented as Magtein. Studied for cognitive function, memory, and age-related cognitive decline. A 2010 Neuron paper demonstrated that increasing brain magnesium enhanced synaptic plasticity and improved learning and memory in rats. Human studies followed, showing improvements in cognitive ability scores in adults with age-related cognitive impairment.
The trade-off: threonate delivers a low amount of elemental magnesium per dose (about 48mg per 2g serving). It’s a brain-targeted form, not a general magnesium replacement. Stack it with glycinate or citrate if you need to address a systemic deficiency.
Magnesium Citrate
Magnesium bound to citric acid. Good bioavailability (better than oxide), relatively affordable, widely available. At standard doses, it’s a solid general-purpose magnesium supplement. At higher doses, it has a laxative effect — which makes it useful for constipation but problematic if GI tolerance is a concern.
This is the form in most bulk magnesium powders. It dissolves well in water and has a mild citrus flavor. For daily magnesium supplementation where cost matters, citrate is the practical choice.
Magnesium Oxide
The cheapest and most common form — and the worst absorbed. Bioavailability is roughly 4%, meaning a 500mg oxide capsule delivers about 20mg of usable magnesium. It’s primarily used as an antacid and laxative. If your current magnesium supplement is oxide and you’re not seeing results, the form is likely why.
Magnesium Taurate
Magnesium bound to taurine. Both magnesium and taurine support cardiovascular function, making this form popular for heart health and blood pressure support. Taurine is a conditionally essential amino acid found in high concentrations in the heart, brain, and retina. The combination may have synergistic cardiovascular benefits, though large-scale human studies specific to magnesium taurate are still limited.
Magnesium Malate
Magnesium bound to malic acid, an intermediate in the Krebs cycle (energy production). Marketed for fatigue and fibromyalgia. Malic acid’s role in ATP production provides a theoretical basis for energy support. Good bioavailability and generally well-tolerated. Some preliminary research supports its use in muscle pain and tenderness, but the evidence base is smaller than for glycinate or citrate.
Magnesium L-Aspartate
A highly bioavailable form that’s been used in European clinical practice for decades. Often found in combination with potassium aspartate for electrolyte balance. Good absorption, mild flavor, and good tolerance. Less commercially prominent in the US market but clinically validated.
How to Choose
Match the form to the goal. Sleep and relaxation: glycinate. Cognitive function: threonate. General supplementation on a budget: citrate. Cardiovascular support: taurate. Energy and muscle function: malate. Avoid oxide if absorption matters (it does). And if you’re addressing a diagnosed deficiency, consult a healthcare provider about dosing — the RDA of 310–420mg is a minimum, not a therapeutic target.
The mineral is the same. The form determines where it goes and how much gets there.