Magnesium Glycinate vs Citrate vs L-Threonate: Which Is Best?

Magnesium is an essential mineral involved in muscle and nerve function, energy production, bone health and cardiovascular function.

Magnesium supplements come in many forms, but three of the most popular are magnesium glycinate, magnesium citrate and magnesium L-threonate.

Although they all provide magnesium, they differ in their gastrointestinal effects, elemental magnesium content and the areas in which they have been studied.

So which one should you choose?

Which magnesium is right for me?

• For sleep or everyday supplementation: magnesium glycinate
• For constipation: magnesium citrate
• For memory and cognition: magnesium L-threonate
• For people prone to loose stools: magnesium glycinate

There is no single "best" magnesium. The most suitable option depends on why you are taking it, your diet, medications and medical conditions.

What is elemental magnesium?

The number on the front of a supplement does not always represent the amount of actual magnesium.

For example, 1,000 mg of magnesium glycinate does not contain 1,000 mg of magnesium.

Magnesium is attached to another compound:

• Glycinate: magnesium + glycine
• Citrate: magnesium + citric acid
• L-threonate: magnesium + L-threonic acid

When comparing products, look for the amount of elemental magnesium provided per dose.

Magnesium glycinate

Magnesium glycinate, also called magnesium bisglycinate, combines magnesium with the amino acid glycine.

It is popular for everyday supplementation because it is generally well tolerated and less likely to cause diarrhoea than magnesium citrate.

It is commonly used for:

• General magnesium supplementation
• Sleep
• Muscle function
• People with sensitive gastrointestinal systems

Magnesium glycinate and sleep

A 2025 randomised controlled trial found that 250 mg of elemental magnesium as magnesium bisglycinate produced a modest improvement in insomnia symptoms compared with placebo.

This suggests magnesium glycinate may help some people with sleep, although it should not be considered a treatment for chronic insomnia.

Pros

• Generally well tolerated
• Low laxative effect
• Suitable for regular supplementation
• Emerging evidence for sleep

Cons

• Usually more expensive than citrate
• Some products combine glycinate with cheaper magnesium forms
• Claims about sleep and anxiety are sometimes exaggerated

Best suited to: people wanting an everyday magnesium supplement, particularly where sleep or gastrointestinal tolerance is a priority.

Magnesium citrate

Magnesium citrate combines magnesium with citric acid.

It is a well-absorbed form of magnesium but also has an osmotic laxative effect, meaning it draws water into the bowel.

For this reason, it can be particularly useful for people who want magnesium supplementation while also experiencing constipation.

It is commonly used for:

• General magnesium supplementation
• Occasional constipation
• People wanting powder or liquid magnesium products

Pros

• Good absorption
• Useful for constipation
• Widely available
• Often relatively inexpensive

Cons

• Can cause diarrhoea
• May cause abdominal cramping or nausea
• Less suitable for people already prone to loose stools

Higher doses used as laxatives can cause significant diarrhoea, dehydration and electrolyte disturbances if overused.

Best suited to: people who want magnesium supplementation and also experience occasional constipation.

Magnesium L-threonate

Magnesium L-threonate is a newer form of magnesium that has been specifically studied for its potential effects on the brain.

It is commonly marketed for:

• Memory
• Cognition
• Focus
• Brain health
• Sleep

Animal research suggests L-threonate may increase magnesium concentrations within the central nervous system, which led to human studies investigating cognition.

Recent clinical trials have reported improvements in some measures of working memory, episodic memory and reaction time.

However, the research is still relatively limited and some studies have been industry funded.

It is also incorrect to say that magnesium L-threonate is the only form of magnesium capable of crossing the blood-brain barrier. Current evidence does not establish this.

Pros

• Most specifically studied for cognition
• Promising early research into memory and cognitive function
• Usually has a low laxative effect

Cons

• Expensive
• Provides relatively little elemental magnesium
• Often requires multiple capsules
• Less human research than more established magnesium forms

For example, approximately 2,000 mg of magnesium L-threonate may provide only around 145 mg of elemental magnesium.

Best suited to: people primarily interested in cognition or memory rather than simply increasing magnesium intake.

Glycinate vs citrate vs L-threonate at a glance

Magnesium glycinate

• Best for: everyday supplementation and sleep
• Laxative effect: low
• Cost: moderate

Magnesium citrate

• Best for: magnesium supplementation and constipation
• Laxative effect: moderate
• Cost: usually lower

Magnesium L-threonate

• Best for: cognition and memory
• Laxative effect: low
• Cost: usually highest

How much magnesium do you need?

Australian recommended daily magnesium intake is approximately:

• Men: 400–420 mg per day
• Women: 310–320 mg per day

These amounts include magnesium obtained from food.

Australia's upper intake level for supplemental magnesium in adults is generally 350 mg per day. This does not include naturally occurring magnesium from food.

Higher doses may sometimes be used under professional supervision.

Side effects and risks

The most common side effects of magnesium supplements are:

• Diarrhoea
• Loose stools
• Abdominal cramps
• Nausea

People with kidney impairment need to be particularly careful because the kidneys are responsible for removing excess magnesium.

Very high magnesium levels can cause weakness, low blood pressure, reduced reflexes, abnormal heart rhythms and, in severe cases, serious toxicity.

Magnesium and medication interactions

Magnesium can reduce the absorption of certain medicines.

Important examples include:

• Tetracycline antibiotics such as doxycycline
• Quinolone antibiotics such as ciprofloxacin
• Bisphosphonates such as alendronate

These medicines may need to be separated from magnesium supplements by several hours.

If you take regular prescription medicines, speak with your pharmacist before starting magnesium.

Check for vitamin B6

Many magnesium supplements also contain vitamin B6.

The Australian TGA has warned that excessive vitamin B6 intake can cause peripheral neuropathy, which may cause tingling, burning or numbness in the hands and feet.

Check all of your supplements to make sure you are not unknowingly taking vitamin B6 from multiple products.

So which magnesium is best?

Choose magnesium glycinate if you want a well-tolerated everyday magnesium supplement or are interested in sleep.

Choose magnesium citrate if you also experience constipation.

Consider magnesium L-threonate if your main interest is memory or cognition and you are comfortable with the higher cost and more limited evidence.

For general supplementation, the elemental magnesium dose and how well you tolerate the product may be more important than choosing the most heavily marketed form.

Disclaimer: This article provides general educational information only and does not replace individual medical advice. People with kidney disease, pregnancy, significant medical conditions or regular prescription medicines should speak with their pharmacist or doctor before starting magnesium supplementation.