Magnesium: What It Actually Does (And Why It's Everywhere Right Now)

The Magnesium Moment

Magnesium is having its moment. If you've spent any time on social media in the last two years, you've probably seen it recommended for sleep, stress, anxiety, cramps, energy, skin, focus, and just about everything else. In 2025, it became the fastest-growing supplement in consumer adoption, with one tracking platform reporting over a 1,000% increase in users adding it to their daily routine.¹ On TikTok alone, wellness creators have turned magnesium glycinate into something of a household name.

Some of the enthusiasm is earned. Some of it has gotten well ahead of the evidence. And when a single nutrient gets positioned as the solution to everything, important nuance tends to get lost. So let's slow down and look at what's actually going on.

What Magnesium Actually Does in Your Body

Magnesium is a cofactor in more than 300 enzymatic reactions. That's not a marketing number. It is involved in energy production (ATP synthesis), protein synthesis, muscle and nerve function, blood sugar regulation, blood pressure regulation, and the structural development of bone.² About 60% of the magnesium in your body is stored in bone, with most of the rest in muscles, soft tissues, and fluids. Less than 1% is in your blood.³

For your nervous system specifically, magnesium plays a role in regulating neurotransmitter signalling. It modulates the NMDA receptor, which is central to neural excitability, and it influences GABA activity, the neurotransmitter most associated with calm and relaxation.⁴ It also helps regulate your hypothalamic-pituitary-adrenal (HPA) axis, which is the system your body uses to manage the stress response.⁵

This is why you'll see it connected to so many different things. It's not that magnesium is a miracle mineral. It's that it's genuinely involved in a huge number of processes, and when levels are low, the effects can show up in multiple places at once.

Are You Getting Enough? The European Picture

The short answer, for many women in Europe, is probably not quite. The Nordic Nutrition Recommendations 2023 couldn't establish a firm recommended intake for magnesium due to limitations in the available evidence, but EFSA sets an adequate intake (AI) of 300 mg/day for women and 350 mg/day for men.⁶ Average dietary intake for adult women in Europe ranges between 250 and 300 mg per day, meaning a meaningful portion of women fall below the threshold.⁶

A large European mapping study that included Denmark found that magnesium intake was generally adequate for most Nordic populations, though Polish and UK women had the highest rates of insufficiency. In Denmark specifically, supplement use contributes an additional 5–12% of daily intake on top of food, which helps close the gap somewhat.⁷ In France, over 75% of women aged 18–54 were found to consume less than the estimated average requirement.⁵

The challenge with magnesium is that outright clinical deficiency (hypomagnesemia) is rare in otherwise healthy people. What's much more common is subclinical insufficiency: your levels aren't low enough to trigger medical alarm, but they're not optimal either. And here's the frustrating part: the standard blood test for magnesium (serum magnesium) only reflects about 1% of your body's total stores. EFSA has acknowledged that there are no truly reliable biomarkers for magnesium status.⁶ You can be technically "normal" on a blood test and still be meaningfully low.

The Sleep and Stress Question

This is the big one. The main reason magnesium has gone viral is the promise that it helps with sleep and anxiety. So what does the evidence actually say?

A 2024 systematic review looked at 15 clinical trials studying magnesium supplementation for anxiety and sleep. Five out of seven anxiety studies showed improvements in self-reported symptoms, and five out of eight sleep studies showed improvements in sleep quality.⁸ A separate RCT from 2024 found that magnesium L-threonate (1 g/day for 21 days) improved sleep duration, deep sleep, and heart rate variability compared to placebo in adults aged 35–55.⁹

That sounds promising, and it is. But there are important caveats. The studies varied significantly in dose, formulation, and duration. Some included additional active ingredients (like vitamin B6), making it hard to isolate magnesium's effect. And the two anxiety studies that showed no benefit were specifically in women with premenstrual and postpartum symptoms, where hormonal factors may have been the primary driver.⁸

The honest assessment: magnesium supplementation appears useful for mild anxiety and sleep quality, particularly in people who are low in magnesium to begin with. If your stress is driven by significant hormonal changes or a clinical anxiety disorder, magnesium alone is unlikely to resolve it. It's a supportive tool, not a standalone treatment.

Magnesium and Women's Health

Beyond sleep and stress, there's a body of research that's specifically relevant if you're a woman. Magnesium plays a role in hormonal regulation through its influence on the pituitary gland, which contributes to progesterone production. Research has found that women with PMS tend to have lower red blood cell magnesium concentrations compared to women without symptoms, regardless of where they are in their cycle.¹⁰

A double-blind study of women aged 24–39 with confirmed PMS found that supplementation with 360 mg of magnesium from day 15 of the cycle through the onset of menstruation significantly improved mood-related premenstrual symptoms.¹¹ Another study found that magnesium combined with vitamin B6 was more effective than magnesium alone for overall PMS symptom reduction.¹² And a 2024 RCT showed that 300 mg of magnesium daily reduced cramps, headache, irritability, and back pain compared to placebo, with the higher dose outperforming 150 mg.¹³

For period cramps specifically, the mechanism is fairly well understood. Magnesium helps relax smooth muscle, including the uterine muscle, and it may reduce the prostaglandins that drive menstrual pain.¹³ A 2017 literature review concluded that magnesium has "an important role for the prevention and the treatment of several conditions relevant to women's health," including dysmenorrhea, PMS, and symptoms of perimenopause.¹⁴

Women with PCOS may benefit as well. Research shows that women with PCOS often have lower serum magnesium levels, and supplementation may help improve insulin sensitivity, which is one of the core metabolic drivers of the condition.¹⁵

Not All Magnesium Is the Same

This is where the supplement industry gets confusing. There are over a dozen commercially available forms of magnesium, and they are not interchangeable. The form determines how much magnesium your body actually absorbs, how well it's tolerated, and what it's best suited for.

Magnesium glycinate (also called bisglycinate) is one of the most bioavailable forms. It's chelated with the amino acid glycine, which helps it absorb through a dedicated peptide transporter in your gut, independently of stomach acid. A 2021 meta-analysis found it was as effective as citrate at raising serum magnesium levels while causing significantly fewer gastrointestinal side effects.¹⁶ The glycine component may also provide its own calming benefits, which is why this form is commonly recommended for sleep and nervous system support.

Magnesium citrate is another well-absorbed organic form. It's widely studied, affordable, and effective for general repletion. It does have an osmotic effect in the gut, meaning it draws water into the intestines, which makes it useful for occasional constipation but potentially uncomfortable for daily use in sensitive individuals.

Magnesium oxide is the form you'll find in most cheap, high-street supplements. It contains a high percentage of elemental magnesium by weight (around 60%), which looks good on a label. But its absorption rate is very low, often under 10%. Most of it passes through your system without being used. If the supplement you're taking right now is magnesium oxide, this might be worth reconsidering.

Magnesium L-threonate is a newer form with some interesting preliminary data on brain bioavailability and cognitive function. It's promising but more expensive and less widely studied for general supplementation.

The point here isn't that one form is universally "best." It's that the form matters, and most consumers don't know to check. If a supplement just says "magnesium" on the label without specifying the form, that's usually a red flag.

What This Means for You

If you're a woman living in Scandinavia and considering magnesium supplementation, here's a grounded perspective on where things stand:

The EFSA adequate intake for adult women is 300 mg/day. The best dietary sources include whole grains, nuts (especially almonds and cashews), seeds (pumpkin and chia are particularly rich), dark leafy greens, legumes, and dark chocolate. Hard water can also contribute meaningful amounts depending on where you live.⁶ A varied, whole-food diet can get you most of the way there.

If you're consistently eating well and feeling fine, you may not need a supplement at all. But if you experience any combination of poor sleep, muscle cramps, tension headaches, PMS symptoms, or persistent low-level stress, subclinical magnesium insufficiency is worth considering as a contributing factor, especially if your diet is low in the foods listed above.

A reasonable supplemental dose for most women is 200–300 mg per day of elemental magnesium, ideally in a well-absorbed form like glycinate or citrate. Research suggests that benefits for PMS and sleep tend to become noticeable after about two months of consistent use, so patience matters.^12,13 The upper tolerable limit set by the European Scientific Committee on Food is 250 mg/day from supplements specifically (on top of food intake), primarily to avoid gastrointestinal side effects.

If you're already taking vitamin D, magnesium becomes especially relevant. As we covered in our article on the Nordic paradox, magnesium is a required cofactor for vitamin D activation. Without sufficient magnesium, your body can't convert vitamin D into its active form, regardless of how much you take.