The short answer: around 300mg of magnesium per day for an adult woman, from food and supplements combined. The longer answer — which is what actually helps you make a decision — depends on what you eat, how active you are, what stage of life you're in, and whether you're trying to maintain a baseline or close a gap.

Most magnesium dosage articles either give you the official number and stop, or pile in so many caveats that you finish the article more confused than when you started. This is a practical guide. Here's what the recommendation is, what it means in real food and supplement terms, and how to think about it across the contexts where it actually changes.

In the UK, the Reference Nutrient Intake (RNI) for adult women is 270mg of magnesium per day.

In the US, the Recommended Dietary Allowance (RDA) is 310mg per day for women aged 19–30 and 320mg per day for women aged 31 and over.

The EU Nutrient Reference Value (NRV) — the figure you'll see on supplement labels — is 375mg.

These look like different numbers but they're answering different questions. The UK RNI and US RDA estimate the average daily intake from food required to meet most adults' needs. The EU NRV is the figure used for nutrition labelling, set slightly higher to provide a useful supplementary buffer. For practical purposes:

A typical adult woman needs roughly 270–320mg of magnesium per day from food and supplements combined. A daily supplement providing 375mg of elemental magnesium covers 100% of the EU NRV and sits within safe long-term supplemental ranges.

These are total daily intake figures. They include what you eat and what you supplement. The two work together.

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A few real-world examples to anchor the numbers:

• 30g pumpkin seeds: ~150mg magnesium

• 100g spinach (cooked): ~80mg

• 30g almonds: ~80mg

• 1 medium avocado: ~58mg

• 100g cooked quinoa: ~64mg

• 100g black beans (cooked): ~70mg

• 30g 70% dark chocolate: ~70mg

• 1 medium banana: ~32mg

• 100g brown rice (cooked): ~44mg

A day that includes oats for breakfast, a handful of nuts mid-morning, a salad with greens and seeds at lunch, and a dinner with whole grains or legumes will land somewhere around 250–350mg of magnesium. That's roughly on target.

The catch: most days for most people don't look like that. National dietary surveys in the UK and US consistently find women fall below the magnesium reference intake more often than men — partly because of smaller average portion sizes, partly because refined and processed foods (which form a large share of modern diets) lose most of their magnesium during processing.

The practical takeaway: a food-first approach is sensible. A daily supplement that closes the residual gap is, for most women, the reliable addition.

Three contexts raise magnesium requirements above the baseline.

Regular training. Intense or sustained exercise increases magnesium turnover by around 20% above sedentary baseline. The body loses more through sweat and excretes more through urine in the hours after a hard session. Women who run, lift, cycle, play racket sports, or train consistently four or more times a week sit at the upper end of the reference range, sometimes a little above it.

Pregnancy. Magnesium needs increase during pregnancy — the UK RNI rises to around 300mg and the US RDA to 350–360mg. This is also a stage where supplement choice should be GP- or midwife-led, not self-directed. Speak to your healthcare provider before starting or changing any supplement during pregnancy.

Breastfeeding. Demand remains elevated through breastfeeding. Again, this is a stage where your GP or midwife should guide supplement choices.

Outside these contexts, the baseline reference intake holds. Age alone doesn't dramatically shift the number — though life-stage factors (perimenopause, post-menopause bone health) make consistency more relevant.

The 375mg figure on a daily magnesium label isn't the total you need — it's the amount the supplement provides. If you're eating an average diet and supplementing 375mg daily, your total intake will land comfortably within the upper-safe range.

Here's why the supplemental number is set where it is:

• The body can only absorb so much at once. Single source, very high doses (above about 350mg supplemental at one time) start to cause digestive issues for many people. 375mg taken in a daily serving — particularly across a combination of well-tolerated forms like glycinate, malate, taurate and Aquamin — sits at the threshold most adults can take comfortably.

• Active losses are real. A 20% increase in demand for training, sweat losses, and urinary excretion means the supplemental number isn't sitting on top of a fully repleted baseline. For most women, especially active ones, the gap is genuine.

• Consistency matters more than a single big dose. Magnesium isn't stored long-term. Daily supplementation builds the baseline; occasional megadoses don't.

If your supplement provides far less than 375mg per serving — many do — read the label carefully and check the elemental magnesium per capsule. "1000mg of magnesium glycinate" sounds impressive but provides only around 100mg of elemental magnesium.

From food, no. Dietary magnesium is well regulated by the body — the kidneys excrete what isn't needed, and food doesn't deliver doses high enough to cause issues.

From supplements, potentially yes, in the sense that very high doses of single source Magnesium can cause digestive symptoms. The most common effect of excess supplemental magnesium is loose stools — usually caused by poorly absorbed forms (oxide, citrate) at high doses, where the unabsorbed magnesium pulls water into the gut.

In practice, supplemental doses of 300–400mg of well-absorbed multi-source forms (eg glycinate, malate, taurate) are widely used and well tolerated long-term in most adults. Stay within manufacturer guidance, and if you experience digestive upset at a particular dose, reduce it.

People with reduced kidney function should not supplement magnesium without medical guidance — the kidneys are how the body clears excess. This is a conversation for a GP, not a blog.

The honest answer: whenever fits your day, as long as it's daily. We've written a full guide on the timing question, but the short version is:

• Mornings if you train early, get afternoon fatigue, or already take a multivitamin at breakfast

• Post-training if you stack sessions or want recovery support in the window

• Evenings if sleep quality is the priority, or you're a heavy evening trainer

Consistency matters far more than the specific slot. Pick one and stick to it.

Either works. With food is slightly gentler on a sensitive stomach and supports the absorption of fat-soluble nutrients in complete formulas (like vitamin D3 and curcumin). Without food is fine if it fits your routine better. The differences in absorption are small enough that consistency matters more than the technicality.

One note: avoid taking magnesium at the same time as high-dose calcium or iron supplements. Both minerals compete for absorption at supplement-level doses. Spread them at least 4 hours apart.

Magnesium deficiency in the clinical sense is uncommon. Sub-optimal magnesium status is much more common, and it tends to show up as low-grade, persistent versions of a small number of patterns:

• Daytime fatigue that doesn't match how well you slept

• Calf or foot cramps after training, or at night

• Muscle tension or twitching in the legs

• Wired-but-tired evenings — struggling to wind down

• Restless sleep, with more middle-of-the-night waking than usual

None of these are specific to magnesium. Sleep quality, training load, stress, hydration and dozens of other factors produce the same patterns. But if several are persistent, a four-to-six-week trial of daily magnesium is a reasonable input to test.

MagnesiumPro provides 375mg of elemental magnesium per daily serving — 100% of the daily recommended intake ( EU NRV) — across four well-absorbed forms (malate, glycinate, taurate, Aquamin). It's paired with plant-based vitamin D3, B6 and B12 (the co-factors magnesium needs to work properly) and functional botanicals (ginger, turmeric, black pepper).

Three capsules with water, daily, with or without food. Built for daily use across an active life.