Last week I wrote about how to read a magnesium label: why the form matters, and why oxide so often disappoints. This week I want to answer the question I get asked most: what will magnesium actually do for me?
The honest answer is that it depends on where you are in life. The magnesium a 32-year-old reaches for to get through a bad week of PMS is doing a different job from the magnesium a 55-year-old takes for her sleep and her bones. Same mineral, different reasons.
So let's go through it stage by stage.
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First, are you low? Signs to look out for
There's no perfect home test for magnesium, and a standard blood test can look normal even when your body's stores are low, because most magnesium sits inside your cells and bones, not in your blood. So the clues are mostly in how you feel.
Early signs of low magnesium can include:
- feeling tired and weak, even after rest
- muscle cramps, especially in the calves at night
- twitching eyelids or muscles
- tension in your neck, shoulders and jaw
- trouble falling or staying asleep
- feeling anxious, irritable or "tired but wired"
- headaches
- loss of appetite or nausea
None of these on their own mean you're low. They can have many causes. But if you tick several, and you're also under stress, drink a lot of coffee or alcohol, eat mostly refined foods, have type 2 diabetes, or take long-term heartburn medicine (PPIs) or diuretics, magnesium is worth looking at.
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In your 30s: periods, PMS and the stress of small children
This is often the decade of broken sleep, busy careers and small children. It's also when many women notice their premenstrual symptoms more.
PMS and mood. Magnesium levels can dip in the second half of your cycle. Several studies have found that magnesium, especially combined with vitamin B6, can ease premenstrual symptoms such as irritability, bloating, breast tenderness and low mood. The studies are small, but the results point the same way, and the combination is gentle.
Period pain. Magnesium helps muscles relax, including the muscle of the womb, and it lowers the chemicals that drive cramping. A review of the research found that magnesium eased period pain better than a placebo, though the trials were small.
Headaches and migraines. Women get migraines about three times as often as men, often around their periods. Magnesium is one of the supplements migraine specialists recommend for prevention. The doses used for migraines are higher than the everyday limit, so do this with your doctor's guidance.
Stress and sleep. If you're running on four hours and a cup of coffee, stress is using up your magnesium faster than usual. This is where magnesium bisglycinate in the evening earns its place.
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Pregnancy and breastfeeding: your needs go up
During pregnancy you need more magnesium: 350 to 360mg a day, compared with 310 to 320mg before. Many pregnant women also get leg cramps at night, and magnesium is often suggested for them. The research on cramps is mixed: some women find it helps, others don't.
| The most important rule here: only take supplements in pregnancy with your doctor or midwife's okay. Check how much magnesium is already in your prenatal vitamin before adding more. (More in Preparing for Pregnancy.) |
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In your 40s: perimenopause, sleep and blood sugar
Perimenopause can start in your early 40s, years before your periods stop. Falling and fluctuating hormones often show up as:
- Sleep that falls apart. Waking at 3am, night sweats, lying awake with a racing mind. Magnesium won't stop hot flushes, but it supports the systems that help you relax and fall back asleep, and many women find it makes their nights a little easier.
- Anxiety and mood swings that seem to come out of nowhere. Magnesium supports the nervous system and is one of the first things I look at.
- Changes in blood sugar and weight. Magnesium is needed for insulin to work properly. People with low magnesium have a higher risk of type 2 diabetes. Magnesium doesn't make you lose weight (a common search, by the way), but it is part of keeping blood sugar steady.
For the food side of this stage, see Nutrition for Hormonal Balance.
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50 and beyond: bones, heart and absorption
After menopause, the focus shifts to protecting what you have.
Bones. About 60% of your body's magnesium is stored in your bones. You need magnesium to make vitamin D work and to build bone properly, alongside calcium. After menopause, bone loss speeds up, so magnesium, calcium and vitamin D work best as a team. (See our diet to help prevent osteoporosis.)
Heart and blood pressure. Studies show magnesium supplements can lower blood pressure slightly. It's a small effect, but it adds up with other healthy habits.
Absorption drops with age. As we get older, we absorb less magnesium from food and lose more through the kidneys. Many of us also take medicines that lower magnesium. That makes the over-50s one of the groups most likely to run low.
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Your quick guide by life stage
| Stage | What magnesium helps with | What to look for |
|---|---|---|
| 30s | PMS, period pain, stress, sleep | Magnesium with B6 for PMS; bisglycinate for sleep and stress |
| Pregnancy and breastfeeding | Higher daily needs, leg cramps | Only with your doctor's okay; check your prenatal first |
| 40s | Perimenopause sleep, anxiety, blood sugar | Bisglycinate in the evening |
| 50+ | Bones, heart, lower absorption | Magnesium together with calcium and vitamin D |
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Lisa's picks for each stage
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For PMS and mood Magnesium, B6 and SaffronViridian · 60 capsules · R720 Made for women's hormonal balance. One capsule gives 200mg of magnesium plus 25mg of vitamin B6 and saffron extract, which has been studied for mood and premenstrual comfort. To fit 200mg into one capsule, it combines three forms: oxide, citrate and bisglycinate.
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For sleep and stress at any age Magnesium BisglycinateViridian · 60 capsules · R395 Pure bisglycinate, 200mg of elemental magnesium in two capsules. The one I take most evenings.
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For bones after 50 Bone Builder with MagnesiumMetagenics · 90 tablets · R695 Calcium, magnesium and vitamin D in one tablet a day.
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For pregnancy and breastfeeding The Tired Mother, Pregnancy and BreastfeedingBundle · R1,915, delivery included A prenatal, magnesium and extra omega-3, with no ashwagandha. Check with your doctor or midwife first.
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Try this week Keep a two-line note on your phone each night for seven nights: how you slept, and how tense your shoulders felt at the end of the day, each scored out of 10. If you start magnesium, keep going with the note. In two to four weeks you'll know from your own numbers whether it's helping. |
With love,
Lisa Chime
Founder of Jannis Health
This article is general information, not medical advice. Speak to your doctor or pharmacist before starting a supplement, especially if you are pregnant, breastfeeding, on medication or managing a health condition.
Frequently asked questions
What are the benefits of magnesium for women?
Magnesium supports sleep, stress, muscle relaxation and energy for women of all ages. It may ease PMS and period pain in your 30s, help with sleep and mood in perimenopause, and support bones and heart health after 50.
What are the signs of magnesium deficiency in females?
Common signs include tiredness, muscle cramps, twitching eyelids, tension in the neck and shoulders, poor sleep, anxiety, headaches and loss of appetite. These can have other causes, so speak to your doctor if they persist.
Is magnesium good for women over 50?
Yes. After menopause, magnesium helps protect bones together with calcium and vitamin D, supports heart health, and matters more because absorption drops with age.
Should I take magnesium glycinate in the morning or at night?
At night if you take it for sleep, stress or cramps. Otherwise any time with food.
How much magnesium should a woman take per day?
Women need 310 to 320mg a day from food and supplements together. Keep supplements at or under 350mg of elemental magnesium a day unless your doctor advises otherwise.