Magnesium has become an internet favorite supplement, lauded as a quick fix for sleep, stress, constipation and even brain health.
But while many Americans don’t get enough from food, people looking to up their intake face another problem: figuring out which kind to take.
Magnesium comes in a laundry list of forms, including glycinate, citrate and L-threonate.
The compound paired with magnesium can affect how readily it dissolves and how much is absorbed, as well as how the product is typically used.
With so many forms to choose from, which kind, and how much, makes sense for your goals?
Millions of Americans don’t get enough magnesium, but not all forms are created equal
First, read the number that matters
Adults generally need 310 to 320mg of magnesium per day for women and 400 to 420mg for men from all sources.
Magnesium assists in 300 functions including muscle and nerve function, blood pressure regulation and energy production.
When taking a supplement, pay attention to the label. On the ‘Supplement Facts’ panel, the amount listed next to ‘magnesium’ is elemental magnesium, the amount of the mineral itself, not the total weight of the compound.
A product may list 2,000mg of magnesium L-threonate, for example, while providing only a fraction of that as actual magnesium.
The National Institutes of Health (NIH) sets an upper limit of 350mg per day from supplements and medications for adults unless a clinician recommends otherwise. Higher supplemental doses can cause diarrhea, nausea and abdominal cramping.
Magnesium from food does not count toward that limit because healthy kidneys can eliminate excess amounts in the urine.
Magnesium glycinate: A popular choice for a more restful night
Magnesium is thought to help relax the nervous system, leading to more restful sleep
Magnesium glycinate, also called magnesium bisglycinate, is commonly chosen by people hoping to sleep better.
Glycinate plays a role in normal nerve and muscle function, which can quiet the body and make it easier to drift off.
In a 2025 randomized, double-blind trial, 155 adults with poor sleep took either 250mg of elemental magnesium from bisglycinate or placebo daily for four weeks.
The magnesium group reported a small but statistically significant improvement in sleep-related symptoms, with greater benefit among people whose diets were lower in magnesium at baseline.
Additionally, a 2021 systematic review and meta-analysis found that magnesium shortened the time it took older adults to fall asleep by about 17 minutes.
Importantly, glycinate should not replace evaluation or treatment for persistent or severe insomnia.
Magnesium citrate: Useful for occasional constipation
Magnesium citrate can act as an osmotic laxative. Magnesium salts that remain in the intestine help retain water in the digestive tract, softening stool and promoting a bowel movement.
That is why liquid magnesium citrate is sold over the counter for occasional constipation. Current labels direct adults to take 6.5 to 10 fluid ounces and say it generally produces a bowel movement within 30 minutes to six hours.
The laxative version is much more concentrated than a typical daily supplement, with some products containing about 290mg of magnesium per fluid ounce.
Taking laxative doses when they are not needed can cause diarrhea and cramping. Repeated use can also disturb fluid and electrolyte balance, and significant diarrhea can contribute to dehydration.
People with kidney disease should not use magnesium laxatives without medical guidance.
Magnesium L-threonate: The pricey ‘brain’ form
L-threonate is often more expensive and heavily marketed for cognition because it was specifically developed with brain health in mind.
In animal studies, magnesium L-threonate increased magnesium in the brain and affected synaptic plasticity, a process involved in learning and memory. That brain-penetration advantage, however, has not been directly demonstrated in humans.
Human research is promising but limited, and there are no strong head-to-head trials showing that L-threonate improves cognition more than cheaper magnesium forms.
In a 2026 trial, 100 adults ages 18 to 45 took 2g of magnesium L-threonate daily, providing 145mg of elemental magnesium, for six weeks.
Participants scored higher on several cognitive tests, including those evaluating working and episodic memory, but not on every test given.
The study, however, was industry funded, so it should be interpreted cautiously.
The price difference can be substantial. Current retail examples put a 30-day supply of L-threonate at roughly $30 to $35, while many glycinate or citrate products can cost closer to $10 to $20 per month, depending on brand and dose.
Magnesium chloride, lactate and aspartate: Good picks for general supplementation
Magnesium chloride, lactate and aspartate are thought to be solid options for general supplementation, but there is not as much evidence linking them to specific health benefits
The NIH lists magnesium chloride, lactate and aspartate, along with citrate, among the more readily absorbed forms.
This makes them great options when the goal is simply increasing magnesium intake, but there is no convincing evidence that they raise magnesium status better than citrate or offer unique benefits for sleep, stress or cognition.
Unlike glycinate, citrate or L-threonate, these forms are not strongly associated with one specific use.
The choice may come down to formulation, cost and tolerance.
How much magnesium should you take?
For general supplementation, focus on elemental magnesium.
The dose depends on why you are taking it, your diet and medical history. Trials have used roughly 250mg for bisglycinate and sleep, 300 mg for citrate absorption, and 145mg to 2g of L-threonate.
Not everyone needs a supplement, and food is an ideal starting point.
One ounce of pumpkin seeds provides about 156mg of magnesium, chia seeds about 111mg and almonds about 80mg. Sprinkle pumpkin seeds over oatmeal, yogurt, salads or soup, stir chia into smoothies or overnight oats and add sliced almonds to salads, curries or grain bowls for a nutrition upgrade.
People with impaired kidney function should not supplement without consulting a healthcare provider because their kidneys cannot properly eliminate excess, causing the mineral to accumulate and lead to toxicity.
Magnesium can also interfere with the absorption of certain antibiotics and osteoporosis medications, so asking your doctor is key.
Johannah Katz, MA, RD, is a registered dietitian based in Florida
