Magnesium and stress: what the research does and doesn't show

The evidence doesn't support magnesium as a reliable way to lower stress or cortisol in a general population. The most relevant trial ran in adults who were both highly stressed and already low in magnesium, had no placebo group, and found that adding vitamin B6 only helped a subgroup with the most severe stress scores.

What the evidence doesn't support

It doesn't support magnesium, at any dose, as something that reliably lowers everyday stress or cortisol in people with normal magnesium levels. It doesn't support "magnesium for cortisol" as a general claim — the one trial that measured stress with a validated scale selected specifically for people who were both stressed and magnesium-low, which is a narrower group than "anyone stressed." And it doesn't support magnesium alone outperforming magnesium plus vitamin B6, except in the subgroup discussed below, where the direction ran the other way.

What the trials found

A 2018 randomized trial gave 264 healthy adults with elevated stress scores and low serum magnesium either 300 mg/day of magnesium alone or 300 mg magnesium plus 30 mg vitamin B6, for 8 weeks. There was no placebo group — both arms received an active treatment. Stress scores, measured on a validated scale, fell by a similar amount in both arms overall (44.9% with B6 added, 42.4% without), and that difference wasn't statistically significant. Only within a subgroup with the most severe baseline stress did adding vitamin B6 produce a significantly larger drop than magnesium alone. Because there was no true placebo arm, this trial can't say how much of the overall improvement in either group was the mineral, the B6, regression toward the mean, or simply time passing during an 8-week study.

The broader anxiety review covered on our anxiety page made the same point about this literature generally: not one of the 18 studies it found used a validated stress measure, which leaves the 2018 trial above as one of the only ones that did — and even that trial had no placebo comparison.

No trial in this literature used magnesium glycinate specifically, and none measured muscle relaxation as a validated outcome, despite how often that phrase appears in marketing copy for this ingredient.

It's also worth being precise about what "low magnesium" meant in the 2018 trial: participants were screened for serum magnesium between 0.45 and 0.85 mmol/L, near or below the low end of the normal range, and for a stress score above a specific cutoff. That is a selected population, not a stand-in for "people who feel stressed." Whether the same 300 mg/day would do anything measurable in someone with normal magnesium status and ordinary daily stress isn't something this trial, or any other in this file, was designed to answer.

Trial	Population	Dose	Placebo arm?	Result
2018 RCT, n=264	Stressed adults, low magnesium	300 mg/day, 8 weeks	No	Both arms improved similarly; B6 helped only the most severe subgroup
2017 review, 18 studies	Anxiety-vulnerable samples	Varied	Mixed	No study used a validated stress scale

Questions people ask

Does magnesium glycinate lower cortisol?

The one trial that measured a stress outcome with a validated scale didn't measure cortisol directly, and it had no placebo group, so it can't establish that magnesium lowered cortisol versus doing nothing. No trial has tested magnesium glycinate specifically against cortisol as an outcome.

How much magnesium glycinate would it take to affect cortisol?

There's no dose established for this, because the trial closest to the question used a form and population (300 mg/day, magnesium-deficient adults with severe stress) that doesn't match a general population taking a standard serving.

Does magnesium glycinate relax muscles?

No trial measured muscle relaxation as an outcome. Magnesium's established roles are in normal muscle function and nervous system function generally, which is a different, narrower statement than a relaxation effect a person would feel.

Can I take a muscle relaxer with magnesium glycinate?

That's a question for a pharmacist or doctor who knows the specific medication, since combining any supplement with a prescription muscle relaxant should be checked rather than guessed at from an article.

Does taking magnesium glycinate with vitamin B6 make a difference?

In the one trial that tested it directly, adding vitamin B6 to magnesium made no measurable difference overall, and only showed an edge over magnesium alone in people whose baseline stress score was already in the severe range. For most of the trial's participants, the two arms tracked each other closely for eight weeks.

When to talk to a doctor

Chronic stress that affects sleep, mood, or daily functioning is worth discussing with a doctor rather than managing with a supplement alone. Magnesium is not a treatment for stress or elevated cortisol, and the trial evidence above doesn't support relying on it as one. If you take medication, are pregnant or nursing, or have kidney disease, talk to a doctor before adding any magnesium supplement.

Related reading: does magnesium glycinate help with anxiety?, magnesium glycinate and ashwagandha, and magnesium glycinate and L-theanine.