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Magnesium Glycinate Side Effects: What to Know

Last reviewed: December 2025

Overview

Magnesium glycinate is one of the best-tolerated forms of magnesium supplements. The chelated form and amino acid carrier result in significantly fewer gastrointestinal side effects compared to magnesium oxide or citrate.

Common Side Effects

Side effects are uncommon at recommended doses but may include:

  • Mild drowsiness — particularly when taken for sleep
  • Slight digestive discomfort — uncommon but possible
  • Soft stools — much less common than with other forms

Less Common Side Effects

At higher doses, some people may experience:

  • Nausea
  • Fatigue or lethargy
  • Mild headache
  • Low blood pressure (feeling lightheaded)

Serious Side Effects

Seek medical attention if experiencing:

  • Signs of hypermagnesemia (magnesium toxicity):

    • Severe drowsiness or confusion
    • Slow or irregular heartbeat
    • Difficulty breathing
    • Severe muscle weakness
    • Very low blood pressure

  • Allergic reaction (rare):

    • Rash, hives, or itching
    • Swelling of face, lips, or throat
    • Difficulty breathing

Toxicity is rare with oral supplementation in people with normal kidney function.

Why Glycinate Is Better Tolerated

Unlike other forms, magnesium glycinate:

  • Does not cause osmotic diarrhea: It doesn’t draw water into the intestines
  • Is absorbed efficiently: Less unabsorbed magnesium remains in the gut
  • Uses an amino acid carrier: Glycine is naturally occurring and well-tolerated

Risk Factors for Side Effects

Higher risk groups include:

  • Kidney disease: Impaired magnesium excretion increases toxicity risk
  • Taking high doses: Exceeding 400 mg elemental magnesium daily without medical guidance
  • Multiple magnesium sources: Using several supplements containing magnesium
  • Certain medications: Those affecting kidney function or magnesium levels

Drug Interactions

  • Antibiotics (tetracyclines, fluoroquinolones): Magnesium reduces absorption—take 2 hours apart
  • Bisphosphonates: Take bone medications first, wait 30+ minutes before magnesium
  • Diuretics: Some increase magnesium loss; others may increase retention
  • Blood pressure medications: Magnesium may enhance hypotensive effects

Sources

  • National Institutes of Health Office of Dietary Supplements — Magnesium
  • Cleveland Clinic — Magnesium Glycinate
  • MedlinePlus — Magnesium in Diet
Last reviewed: December 2025