Snooze University

Which Form of Magnesium is Best for Sleep? (Science-Backed)

by Dale Cudmore | Updated: May 23, 2021

Magnesium oxide, glycinate, citrate...

The list goes on.

There are many types of magnesium supplements out there, and from anecdotal reports, they are not all reported equally.

While there isn’t a ton of academic research on magnesium and sleep, there is some out there. We’ll summarize it in this short post.

Does Magnesium Improve Insomnia?

Is there any scientific reason to believe that magnesium supplements improve sleep quality?

It turns out that there’s a bit out there. 

One review found 3 high quality randomized control trials that looked at the impact of magnesium supplementation on sleep (1). They found:

Pooled analysis showed that post-intervention sleep onset latency time was 17.36 min less after magnesium supplementation compared to placebo.

In other words, subjects fell asleep just over 17 minutes faster than the control group after taking a magnesium supplement.

SummaryMagnesium supplements are cheap and easy to find. Early research shows that it’s effective in people who have insomnia and a magnesium deficiency. That might not be enough for a doctor to prescribe it, but that may change as more research is done.

How Does Magnesium Improve Sleep?

Currently, it appears that no one knows exactly why magnesium supplements can have such a positive effect on sleep.

However, we do know a few things.

Low magnesium levels are linked to low melatonin levels (2). Same goes for zinc and folate as a side note.

Magnesium is involved in neuroendocrine regulation, which is important for sleep governance.

If you really want to get into it, the image below lays out the potential effect of magnesium on sleep, but it’s not that important if you’d like to just move ahead.

Why Does the Form of Magnesium Matter?

Next comes the question: why not just buy the first magnesium supplement you can find?

Well if you read different people’s stories, you’ll find that they say that some forms of magnesium make their sleep better, while others have the opposite effect. Not exactly a scientific study, but it’s the best we have for now.

I propose 2 main reasons to explain why the form of magnesium matters:

  1. Bioavailability - Some forms of magnesium absorb better than others. If you can’t absorb magnesium, it obviously can’t help.
  2. Reaction to specific anion - Magnesium is a cation in its elemental form, so it needs to be paired with an anion like gluconate or oxide to make a usable form for a supplement. Some of these pairs can cause adverse effects.

Let’s look at this in a bit more detail.

Bioavailability of Different Magnesium Forms

One study I found looked at this in great detail.

Here’s a partial chart from it that compares different types of magnesium (3):

Of the forms that are typically found in supplements, the ones that are considered “good” in terms of bioavailability are:

  • Magnesium chloride
  • Magnesium citrate
  • Magnesium gluconate
  • Magnesium glycinate

On the other hand, the forms that don’t absorb so well are:

  • Magnesium oxide
  • Magnesium carbonate

Magnesium oxide is often found in cheap supplements. Glycinate and citrate are the forms that are easiest to find in most cases that absorb well.

Reactions to Different Forms

Creating these supplements is basic chemistry.

For example, to make magnesium citrate, you combine magnesium with citrate.

It turns out that GI distress and diarrhea are common with magnesium supplements, especially if you overdo them (which can be dangerous). The study mentioned just above went into more detail about this.

Everyone reacts to different substances differently, however, magnesium glycinate is usually least likely to cause side effects.

Magnesium citrate is known to have a laxative effect if you take too much.

Pairing Magnesium With Other Sleep Aids

Finally, you might come across magnesium supplements that have other sleeping aids added to them.

This can be a good thing, but also introduces another element that might help or hinder sleep quality.

One study found that a magnesium-melatonin-vitamin B complex had a beneficial effect on insomnia patients regardless of the cause of their insomnia (4).

The Quality of Magnesium Supplements Vary

The quality of supplements varies widely.

Many supplements don’t contain what the label says they do. Some contain less of the main ingredient than they should, while others contain other filler ingredients that can cause side effects.

For example, one research team analyzed over the counter melatonin supplements (5). They found:

Melatonin content did not meet the label within a 10% margin of the label claim in more than 71% of supplements and an additional 26% were found to contain serotonin.

While I couldn’t find a specific study on magnesium supplement quality, I would imagine that it’s a similar situation.

Price doesn’t necessarily guarantee a high quality supplement, but a high priced product is probably more likely to be high quality.

Look for brands who have their products tested for purity by third party labs (still not perfect, but better than nothing).

Summary: Which Form of Magnesium is Best?

In short, we’ve seen that magnesium supplements likely do improve sleep in those that are deficient in magnesium.

Different forms of magnesium have different levels of bioavailability, and may cause side effects that interfere with sleep in some people (depends on the individual and amount consumed).

If I had to rank the forms that are often found in supplements (this is very unofficial) from best to worst, the top forms of magnesium would be:

  • Magnesium glycinate
  • Magnesium citrate
  • Magnesium gluconate
  • Magnesium chloride

But as mentioned, one form may work for one person, while having no effect (or a negative one) for someone else.

Finally, if you are taking any other supplements or medications, ask your doctor before taking a magnesium supplement. Almost any supplement can interact with others in unexpected ways, and depending on your specific situation, it might not be a good idea to consume additional magnesium.


  1. Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis
  2. Dietary factors and fluctuating levels of melatonin
  3. Bioavailability and pharmacokinetics of magnesium after administration of magnesium salts to humans
  4. The Effects of Magnesium – Melatonin - Vit B Complex Supplementation in Treatment of Insomnia
  5. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.