The Hungry Pharmacist

Magnesium is one of the most talked-about minerals in nutrition and supplementation—and for good reason. It plays a role in over 300 enzymatic reactions in the human body, influencing muscle contraction, nerve function, energy metabolism, heart rhythm, and even mood and sleep.

Yet one question keeps coming up again and again:

Which form of magnesium is actually the best?

The short answer: there is no single “best” magnesium.
The long answer (and the useful one): the best form depends on your goal, tolerance, and the specific indication.

1. Magnesium Bioavailability – What Does It Really Mean?

Bioavailability refers to how well magnesium is absorbed from the gut and becomes available for use in the body.

From scientific literature, one pattern is very consistent:

Organic magnesium salts = better absorption

Magnesium bound to organic acids tends to dissolve better in water and is generally absorbed more efficiently than poorly soluble inorganic forms.

Forms with generally higher bioavailability:

• Magnesium citrate
• Magnesium chloride
• Magnesium lactate
• Magnesium aspartate
• Magnesium (bis)glycinate (chelated form)

Lower bioavailability (but still useful):

• Magnesium oxide

This doesn’t mean magnesium oxide is “bad”—it simply behaves differently in the body.

2. Magnesium Oxide: Low Absorption, High Local Effect

Magnesium oxide contains a high percentage of elemental magnesium, but it dissolves poorly in the gut.

What does that mean in practice?

• Less magnesium enters the bloodstream
• More magnesium stays in the intestines

That’s exactly why magnesium oxide (and related forms like magnesium hydroxide) is often used for:

• Constipation
• Short-term bowel regulation

If your goal is raising magnesium levels, oxide is usually not the first choice.
If your goal is a laxative effect, it can be very effective.

3. Magnesium Citrate: The All-Rounder

Magnesium citrate is one of the best-studied and most commonly recommended forms.

Why is it so popular?

• Good water solubility
• Reliable absorption
• Affordable and widely available

Common indications:

• Magnesium deficiency
• Muscle cramps
• Migraine prevention
• General supplementation

At higher doses, citrate can cause looser stools, which may be a benefit or a drawback depending on the situation.

4. Magnesium Glycinate (Bisglycinate): Best for Tolerance

Magnesium bisglycinate is a chelated form, meaning magnesium is bound to the amino acid glycine.

Advantages:

• Excellent gastrointestinal tolerance
• Minimal laxative effect
• Suitable for long-term use

Often chosen for:

• Stress and anxiety
• Sleep support
• People with sensitive digestion
• Night-time supplementation

From a practical standpoint, this is often the “safest” choice for daily magnesium supplementation.

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5. Magnesium and Specific Indications

Muscle cramps & neuromuscular symptoms

• Citrate
• Aspartate
• Glycinate
  Evidence is mixed in the general population, but benefits are more consistent in people with low magnesium intake or increased needs (e.g. athletes, pregnancy).

Migraine prevention

Magnesium supplementation is supported by clinical guidelines as a preventive option.

• Citrate and oxide are most commonly studied
• Glycinate is often preferred if GI side effects occur

Stress, anxiety, sleep problems

No single form is “proven superior,” but in practice:

• Magnesium glycinate is often preferred due to calming glycine and good tolerability
• Consistency matters more than the exact salt

Constipation

• Magnesium citrate
• Magnesium hydroxide / oxide

Here, lower absorption is actually an advantage, because magnesium draws water into the intestines.

6. How to Choose the Right Magnesium (Simple Rule)

Ask yourself one question:

What is my primary goal?

•  Raising magnesium levels → Citrate or Glycinate
•  Sensitive stomach / long-term use → Glycinate
•  Constipation → Citrate or Oxide
•  Migraine prevention → Citrate (switch if not tolerated)

Tip from practice:
If diarrhea occurs, lower the dose, split it into two intakes, or change the form.

7. Safety and Drug Interactions

Magnesium supplements are generally safe, but important notes:

• Kidney disease → magnesium should only be used under medical supervision
• Magnesium can reduce absorption of:
  • Antibiotics (tetracyclines, fluoroquinolones)
  • Levothyroxine
  • Bisphosphonates

⏱️ Keep a 2–4 hour gap between magnesium and these medications.

There is no “one-size-fits-all” magnesium. What matters the most are bioavailability, indication and the tolerance matters.

If you have cramps, train hard or want to raise your magnesium levels you should choose magnesium as citrate or glycinate.