Magnesium Dosage: How Much to Take, Side Effects, and Interactions (2026)

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Person holding magnesium supplement bottle and pills illustrating magnesium dosage, side effects, and medication interactions — Magnesium dosage guide: how much to take, common side effects, and important medication interactions.

For most adults, a practical supplement trial is 100–200 mg of elemental magnesium per day. Take it with food if your stomach is sensitive. If you get diarrhea, reduce the dose, split it, or switch to a gentler form (often glycinate). Avoid high doses unless medically supervised.

1) The most important thing: “Elemental magnesium”

Magnesium supplements come in different forms (glycinate, citrate, oxide, etc.). But for dosing, what matters is elemental magnesium—the actual amount of magnesium your body receives.

How to read the label (fast)

Look for a line like:

Magnesium (as magnesium glycinate/citrate/oxide) — X mg

That X mg is commonly the elemental magnesium amount. If the label is unclear or only lists the compound amount, choose a different brand or confirm with a pharmacist.

2) Common supplement dosage ranges (practical guide)

These ranges are typical starting points, not medical prescriptions.

Daily support (general wellness)

100–200 mg elemental magnesium per day

Good for people who want a simple, low-risk starting point and want to test tolerance.

Sleep support or evening routines

100–200 mg elemental magnesium per day, often taken in the evening

Keep the dose lower if you’re sensitive to GI side effects.

Constipation support

Some people use magnesium for bowel regularity. If constipation is part of the problem:

Start with a low dose and adjust slowly.

Important: Magnesium used as a laxative may involve different dosing than daily supplementation. If you’re using magnesium specifically as a laxative, follow the product directions or professional advice.

3) Best timing: when to take magnesium

With meals: often improves stomach tolerance
Split dosing: if one dose causes diarrhea or cramping (half earlier, half later)
Evening: popular for sleep/stress routines

How long to evaluate results

If you’re using magnesium for general support, give it 2–4 weeks to judge results, assuming you tolerate it well.

4) Side effects: what to expect

Most common (dose-related)

Diarrhea
Nausea
Stomach cramps

What to do

Reduce the dose
Split the dose
Switch to a gentler form
Take it with food

Warning signs (get medical help)

Seek urgent help if you experience:

severe weakness or confusion
fainting or very low blood pressure symptoms
irregular heartbeat symptoms

Magnesium toxicity is uncommon from normal supplement use in healthy people, but the risk increases with kidney disease and very high supplemental intakes.

5) Who should be careful (or avoid supplements)

Talk to a healthcare professional before taking magnesium supplements if you have:

Kidney disease
multiple chronic conditions
a long list of medications
pregnancy or breastfeeding (needs vary)

If your kidneys cannot clear magnesium effectively, magnesium levels can rise too high.

6) Medication interactions (don’t skip)

Magnesium can reduce absorption of certain medications if taken at the same time. Common categories include:

some osteoporosis medications (bisphosphonates)
some antibiotics
some diuretics (may increase or decrease magnesium loss depending on the type)
long-term acid reflux/ulcer medicines (may contribute to low magnesium over time)

Simple spacing rule

As a general approach, avoid taking magnesium at the exact same time as these medicines. Separate dosing by several hours based on your prescription label or clinician advice.

7) Recommended intake vs supplement upper limits (important)

There are two different ideas people often mix up:

A) Recommended intake (total magnesium from food + supplements)

Health authorities publish recommended intakes for magnesium by age and sex. This is about total daily intake, not “how much supplement to take.”

B) Upper limit (supplements/medications only)

Some authorities set an “upper limit” for magnesium from supplements and medications because higher amounts commonly cause diarrhea and stomach upset.

Practical takeaway

If you’re supplementing for general support, staying near 100–200 mg elemental/day is a conservative, commonly used range.
Avoid pushing high supplemental doses unless medically supervised.