Best Magnesium Supplements Compared: Threonate vs Glycinate vs Citrate

Magnesium is one of the most important minerals in the human body, involved in over 300 enzymatic reactions ranging from energy production to DNA synthesis. Yet an estimated 50% of Americans consume less than the recommended daily amount. If you have decided to supplement, you will quickly discover that not all magnesium supplements are the same. The three most popular forms—magnesium threonate, magnesium glycinate, and magnesium citrate—each offer different benefits, bioavailability profiles, and ideal use cases.

This guide provides a thorough, evidence-based comparison so you can choose the right form for your goals.

Why Magnesium Form Matters

Magnesium supplements pair the mineral with a carrier molecule (an amino acid, organic acid, or other compound) that affects three things:

1. Bioavailability — How much of the magnesium your body actually absorbs.
2. Tissue targeting — Where in the body the magnesium accumulates most.
3. Secondary benefits — The carrier molecule itself can have biological effects (e.g., glycine promotes relaxation; threonic acid crosses the blood-brain barrier).

Choosing the wrong form can mean you are paying a premium for a benefit you do not need, or missing out on the specific support you are looking for.

Magnesium Threonate (MgT / Magtein)

What It Is

Magnesium L-threonate is a patented compound (Magtein) developed by researchers at MIT. Threonic acid is a metabolite of vitamin C, and when bonded to magnesium it creates a uniquely brain-permeable form. A landmark 2010 study in Neuron (PMID: 20152124) showed that magnesium threonate increased cerebrospinal fluid magnesium concentrations far more effectively than other forms tested (including citrate and chloride).

Best For

• Brain health and cognitive function
• Sleep quality (the form recommended in the Huberman sleep cocktail)
• Age-related cognitive decline
• Anxiety and stress

Clinical Evidence

A 2022 randomized, double-blind trial (PMID: 34621186) found that 1,500–2,000 mg of magnesium threonate daily improved sleep quality and reduced sleep latency in older adults. Another study in the Journal of Alzheimer's Disease (PMID: 26519439) reported improvements in executive function and working memory in cognitively impaired adults supplementing with MgT.

Dosage

The standard dose is 1,500–2,000 mg of magnesium L-threonate per day (providing roughly 100–145 mg elemental magnesium). This is typically split into two doses or taken entirely before bed.

Drawbacks

The elemental magnesium content is lower per gram compared to citrate, so it is not ideal for correcting a systemic magnesium deficiency. It is also the most expensive of the three forms.

Magnesium Glycinate

What It Is

Magnesium glycinate (also called magnesium bisglycinate) pairs magnesium with the amino acid glycine. Glycine itself is an inhibitory neurotransmitter that promotes relaxation and has its own sleep-enhancing properties. A 2015 study in Neuropsychopharmacology (PMID: 25533534) demonstrated that 3 g of glycine before bed improved subjective sleep quality and reduced next-day fatigue.

Best For

• Sleep and relaxation (excellent budget alternative to threonate)
• Anxiety and muscle tension
• People with sensitive stomachs (very gentle on the GI tract)
• General magnesium repletion

Bioavailability

Glycinate is one of the most bioavailable forms of magnesium. A study published in the Journal of the American College of Nutrition (PMID: 14596051) showed that organic magnesium chelates like glycinate had significantly higher absorption compared to inorganic forms like oxide.

Dosage

200–400 mg of elemental magnesium from glycinate, typically taken in the evening. This is the form Andrew Huberman recommends as an alternative to threonate.

Drawbacks

It does not cross the blood-brain barrier as effectively as threonate, so it may not provide the same targeted cognitive or neuroprotective benefits. Some glycinate products on the market are "buffered" with magnesium oxide, which reduces quality.

Magnesium Citrate

What It Is

Magnesium citrate pairs magnesium with citric acid. It is one of the most common and affordable forms of supplemental magnesium, widely available in capsules, powders, and liquid form (Natural Calm is a popular brand).

Best For

• Correcting magnesium deficiency (higher elemental Mg per serving)
• Constipation relief (osmotic laxative effect)
• Muscle cramps and recovery
• Budget-friendly magnesium supplementation

Bioavailability

Citrate has moderate-to-good bioavailability—better than oxide but slightly lower than glycinate in some comparisons. A 2003 study (PMID: 14596051) found organic salts like citrate were absorbed better than inorganic ones.

Dosage

200–400 mg of elemental magnesium per day. Start at the lower end if you have a sensitive stomach, as citrate can cause loose stools at higher doses due to its osmotic effect in the intestines.

Drawbacks

The laxative effect can be a pro or con depending on your needs, but it makes citrate a poor choice for people with IBS-D or those prone to diarrhea. It also lacks the targeted brain benefits of threonate and the calming amino acid bonus of glycinate.

Comparison Table: Threonate vs Glycinate vs Citrate

Here is a quick-reference comparison of the three forms:

• Brain bioavailability: Threonate (high) > Glycinate (moderate) > Citrate (low)
• Sleep support: Threonate (excellent) = Glycinate (excellent) > Citrate (moderate)
• GI tolerance: Glycinate (best) > Threonate (good) > Citrate (may cause loose stools)
• Elemental Mg per serving: Citrate (high) > Glycinate (moderate) > Threonate (low)
• Cost: Citrate (cheapest) < Glycinate (moderate) < Threonate (most expensive)
• Best use case: Threonate (brain/cognition), Glycinate (sleep/relaxation), Citrate (deficiency/constipation)

Can You Combine Multiple Forms?

Yes, and many people do. A common approach is to take magnesium threonate in the evening for its cognitive and sleep benefits and magnesium citrate or glycinate earlier in the day for general repletion. Just be mindful of your total elemental magnesium intake—the upper tolerable limit from supplements is generally considered to be 350 mg per day by the NIH, though many functional medicine practitioners use higher doses under supervision.

Other Magnesium Forms Worth Knowing

Magnesium Taurate

Pairs magnesium with taurine, an amino acid with cardiovascular benefits. Research suggests it may help support healthy blood pressure and heart rhythm. A good choice for cardiovascular-focused supplementation.

Magnesium Malate

Pairs magnesium with malic acid, which plays a role in the Krebs cycle (energy production). Sometimes recommended for people with fibromyalgia or chronic fatigue, though evidence is limited.

Magnesium Oxide

The cheapest and most common form, but also the least bioavailable (only about 4% absorption). Primarily useful as an osmotic laxative. Not recommended for correcting deficiency or achieving therapeutic brain effects.

How to Choose the Right Magnesium

Use this decision framework:

1. Primary goal is sleep or brain health? Choose magnesium threonate.
2. Want sleep support on a budget? Choose magnesium glycinate.
3. Correcting a deficiency or dealing with constipation? Choose magnesium citrate.
4. Heart health focus? Consider magnesium taurate.
5. Not sure? Start with glycinate—it is the most versatile and best tolerated.

For a protocol that uses magnesium threonate as part of a complete sleep system, read our Huberman Sleep Cocktail guide.

Frequently Asked Questions

Which magnesium is best for anxiety?

Magnesium glycinate is generally considered the best form for anxiety, as the glycine component has its own calming properties. Magnesium threonate is also a strong option since it directly increases brain magnesium levels. Both are superior to citrate for this purpose.

Can I take magnesium every day?

Yes. Magnesium is an essential mineral and daily supplementation is safe for most people. The NIH recommends 310–420 mg of total elemental magnesium daily for adults (from food and supplements combined). If you have kidney disease, consult your doctor before supplementing.

What time of day should I take magnesium?

For sleep, take it 30 to 60 minutes before bed. For general health, timing matters less. Some people split their dose between morning and evening. Magnesium can be taken with or without food, though taking it with a meal may reduce any chance of stomach upset.

Is magnesium oxide worth taking?

For most people, no. Its bioavailability is extremely low (around 4%). You would need to take a very large dose to get the same benefit as a smaller dose of glycinate or citrate. It is mainly useful as a laxative.

Does magnesium help with muscle cramps?

Evidence is mixed but generally supportive, especially in people who are deficient. A systematic review (PMID: 32572757) found modest benefit for pregnancy-related leg cramps. Citrate and glycinate are the most commonly recommended forms for muscle cramps.