Magnesium is having a moment. It’s become the go-to for so many issues over the last couple years that it seems to be the answer for almost every malady. And because of that the options for magnesium supplements have exploded in the supplements aisle.
When there were just a handful of options a few years ago, it feels like there are hundreds now. And a lot of the time you don’t know what’s real or not.
My endocrinologist told me that my magnesium wasn’t that low, so I didn’t really need a supplement. But many people do need it. How do you know? Well, it can show up in many specific ways. We always recommend asking your doctor first. Especially if you have any of the symptoms below.
“Magnesium deficiency is on the rise and of great concern,” says Ali Miller, a registered dietitian who focuses on food-as-medicine. “We see 50 to 70% of the US population with a deficiency, so much so that it’s becoming a public health concern.”
The Sneaky Symptoms
“Muscle cramps and spasms: magnesium is crucial for muscle relaxation, balancing calcium and potassium in muscle cells,” says Dr. Sethi, a physician who lists it first among the signs he tells patients never to ignore.
The eye twitch is the one I know personally. I’ve definitely had it, not totally sure what to blame it on, but it’s one of those things that just sort of comes and goes. It feels like it’s almost stress related, that’s what we always blame it on.
The others dietitians flag: night-time calf cramps, trouble staying asleep, anxiety, migraines, PMS, heart palpitations, stubborn constipation, restless legs, and afternoon energy crashes. One alone isn’t a diagnosis. Three or more together is the pattern.
1. Night-time calf cramps
What it feels like: These can be the worst. One minute you’re laying there dreaming about something lovely and the next your calf turns into a huge, seizing knot. It bolts you awake and you have to try to loosen it before you can fall back asleep.
What the research says: This is the one everyone blames on magnesium, and it has the weakest support. A Cochrane review of the randomized trials concluded magnesium is unlikely to provide meaningful cramp relief in older adults.
What to do: Try food first. Drink more fluids than you have been drinking. Then ask your doctor. Food first.
“muscle cramping, tension, or twitching … maybe an eye twitch” — Ali Miller, RD, on magnesium deficiency (1:50)
2. Trouble staying asleep
What it feels like: Are you in the sleep/wake cycle? You have no problem falling asleep, but you wake up between two and four am and can’t get back to sleep for hours.
What the research says: A meta-analysis found a benefit for insomnia in older adults but rated the underlying studies low quality. A 2024 trial of magnesium L-threonate reported better sleep and next-day functioning.
What to do: Magnesium glycinate is the standard sleep form; L-threonate is the one in that 2024 trial.
“an ample amount of magnesium can counteract that cortisol, which drives that middle of the night waking” — Ali Miller, RD, on magnesium deficiency (2:22)
3. Anxiety
What it feels like: Everyone has anxiety, but are you having physical reactions to anxiety in addition to the mental? These can be anything from a tight chest, a clenched jaw or shallow breathing?
What the research says: Reviews find magnesium suggestive of benefit in anxiety-prone people while calling the evidence quality poor.
What to do: Give glycinate a try. There’s not a ton of evidence here, but if your doctor says you are OK to, it is worth a try.
“magnesium works as a mineral to buffer stress in the body … when deficient, we just don’t have that counterbalance” — Ali Miller, RD, on magnesium deficiency (3:19)
4. Migraines
What it feels like: Migraines can be so debilitating. They are awful headaches that can focus on one side of your head, and even give you some sensitivity to light and sounds.
What the research says: One of the better-supported uses. Systematic reviews back magnesium for migraine prevention rather than for stopping an attack in progress.
What to do: The thing about magnesium is that it won’t stop a migraine. Meaning, if you have a migraine, it’s too late. But taking it daily may help prevent future migraines. Discuss your dosage with your doctor.
“Magnesium does serve as a vasodilator to actually open the blood vessels” — Ali Miller, RD, on magnesium deficiency (3:42)
5. PMS
What it feels like: PMS is never good. But if you have extra amounts of bloating and breast tenderness it may be a sign you’re low on magnesium.
What the research says: Thinner than it looks. Magnesium is mostly studied alongside vitamin B6 rather than on its own, so it is hard to separate the two.
What to do: Worth noting: B6-and-magnesium combinations are the ones that are most tested.
6. Heart palpitations
What it feels like: Typically palpitations feel like a flutter or a skipped beat. They can be scary.
Side story: The first night my partner and I took magnesium I felt fine, but she felt like her heart was racing (which is ironic because heart palpitations can be a sign that you are low on magnesium).
We weren’t sure if it was the magnesium that caused it, but we erred on the safe side and paused it for a while. It’s always good to get your blood work done before adding it.
What the research says: Studied in a nonrandomized trial only. The evidence is thin.
What to do: Do not self treat heart palpitations. See your doctor instead of trying to manage them yourself.
“maybe we’re actually having physical symptoms of like heart palpitations” — Ali Miller, RD, on magnesium deficiency (3:19)
7. Stubborn constipation
What it feels like: If you have fewer than three bowel movements a week, this is a sign you have constipation.
What the research says: The strongest evidence of the nine. A randomized placebo-controlled trial found magnesium oxide significantly improved both bowel frequency and quality of life, with no severe adverse events.
What to do: This is where the type of magnesium matters: oxide and citrate pull water into the bowel. Glycinate doesn’t (and you want more water in your bowel!)
8. Restless legs
What it feels like: Do you need to keep moving your legs while you’re at rest? (This can be either in bed, lounging or sitting.) And this is different than the thing some people do when they rub their legs or feet together as a form of getting cozy in bed. This is an urge that is typically only relieved by walking.
What the research says: An open-label pilot of magnesium citrate showed improvement, but the authors themselves call for a placebo-controlled trial before anyone draws conclusions.
What to do: Citrate was the form that was studied.
9. Afternoon energy crashes
What it feels like: That hard drop that usually happens in the mid afternoon (between 2-4pm.)
What the research says: We could not find a single clinical trial testing magnesium for afternoon fatigue. It is mechanistically plausible — magnesium is a cofactor in ATP production — but plausible is not the same as demonstrated.
What to do: Before trying magnesium, try food here first. Pumpkin seeds, cooked spinach and black beans are great options.
Beyond the checklist
The list above are the symptoms to keep an eye out for. The rest of this article is a bit of a deeper dive into what else to know as well as what actually moves your number.
The Sleep Connection
This is the one I know best. Sleep has always been difficult, you have those stretches where you’re sleeping great, and then the next thing you know you’re waking up every night at three AM and you just can’t go back to sleep. I should probably actually try magnesium more for that.
The thing everyone likes to do now is get sunlight in your eyes in the morning, that’s a Huberman thing, supposed to reset your circadian rhythms and, oddly enough, help you sleep at night.
Funny enough, when I’ve worked out extra hard to wear myself out and sleep better, I always end up more awake than normal. Doesn’t make sense to me logically, but here we are.
Why the Blood Test Misses It
I’ve made my own peace with this gap. When the blood work comes back fine but you still feel off, sometimes I just chalk it up to getting older.
Compare how you felt at twenty-two to fifty-two and fifty-two is never gonna win on energy. So I look at blood work as an internal check, to catch something before it gets out of hand, not as a readout of how you feel day to day.
Unless you’ve got an acute issue, it’s almost never tied to how you feel. You hear about people running marathons who were doing great and then keel over, and the right blood work might have caught it.
With magnesium it’s worse than usual, because a standard serum test only sees the sliver in your blood, not what’s drained from muscle and bone.
Food First, Then Form
Food moves the number fastest, pumpkin seeds, cooked spinach, black beans, almonds, dark chocolate. On supplements, “we want to be looking for magnesium bis-glycinate as the optimal form to supplement with,” Miller says, the same glycinate in most sleep-and-cramp formulas.
But if there’s one habit worth more than any single supplement, it’s vetting what you buy. We once bought one late, hoping it’d help with certain things, and it just didn’t.
There was a study where everyone assumed fish oil was all great and all the same, and then they cut a bunch of samples open and a lot were kind of rancid inside.
You never know, so you’ve gotta be super vigilant. Even with something proven good for you, ask your doctor which ones they recommend, and I don’t mean a doctor on Instagram promoting a product they make money off of.
I mean your own doctor. When you find out which ones they personally take, that’s a great sign of which ones you should be taking.
The nine signs, ranked by evidence
Every claim above in one place, strongest evidence first — not in the order these symptoms usually get listed online. Verdicts link to the study.
| Sign | What the research shows | Verdict |
|---|---|---|
| Stubborn constipation | Beat placebo on bowel frequency and quality of life | Strong |
| Migraines | Backed for prevention, not for stopping an attack | Moderate |
| Trouble staying asleep | Benefit found, underlying studies rated low quality | Mixed |
| Anxiety | Suggestive in anxiety-prone groups; evidence quality poor | Mixed |
| Restless legs | Open-label pilot only; no placebo-controlled trial yet | Preliminary |
| Heart palpitations | Nonrandomized trial only | Thin |
| PMS | Mostly studied with vitamin B6, not alone | Thin |
| Night-time calf cramps | Unlikely to help older adults | Not supported |
| Afternoon energy crashes | No clinical trials found | Not studied |
Kaelyn Johnson is a Registered Dietitian from Southern California who has worked as a clinical dietitian and is now a freelance writer. She has written for WebMD, produced an e-book, and written case studies for healthcare practitioners.
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