Magnesium Glycinate and Urinary Frequency
Magnesium glycinate supplementation does not typically cause increased urination or frequent urination in most people. Unlike diuretic medications or poorly absorbed magnesium salts that can have osmotic effects, magnesium glycinate is well-absorbed and does not directly increase urine production 1.
Why Magnesium Glycinate Doesn't Increase Urination
Magnesium glycinate is an organic magnesium salt with superior bioavailability compared to inorganic forms like magnesium oxide. The glycinate form is efficiently absorbed in the gastrointestinal tract, meaning less remains in the intestinal lumen to draw water and create osmotic effects 1. This distinguishes it from magnesium oxide, which is poorly absorbed and commonly causes diarrhea due to its osmotic properties 1.
Key Mechanistic Differences
Magnesium itself does not act as a diuretic. While diuretic medications increase urinary excretion of magnesium (along with sodium, potassium, and water), magnesium supplementation does not reciprocally increase urine volume 2, 3.
Magnesium supplementation increases urinary magnesium excretion, not total urine volume. Studies show that magnesium supplements (250-500 mg/day) significantly increase the amount of magnesium in urine, but this reflects the body excreting excess magnesium rather than producing more urine 4.
The relationship between magnesium and urination is one-directional. Diuretics cause magnesium loss in urine by increasing overall urine production 2, 3, but magnesium supplementation does not cause the reverse effect of increasing urine production.
What Actually Happens With Magnesium Supplementation
When you take magnesium glycinate, your body absorbs what it needs and excretes the excess through the kidneys. Research demonstrates that magnesium supplementation (250-500 mg/day) increases urinary magnesium from approximately 47 mg/day to 87 mg/day, with 88% of supplemented patients achieving adequate urinary magnesium levels 4.
Expected Urinary Changes
Urinary magnesium concentration increases, not urine volume. The magnesium content of urine rises substantially with supplementation, but this occurs within normal urine volumes 4, 5.
Magnesium glycinate may increase urinary citrate levels. Studies show that magnesium supplementation (21 mEq daily for one month) significantly increases urinary citrate excretion, which is beneficial for preventing kidney stones, but does not increase urine frequency 5.
When taken with meals, magnesium absorption improves further. Administering magnesium salts with food increases urinary magnesium by 92-96 mg/day and citrate by 218-226 mg/day, without reports of increased urination frequency 6.
Common Pitfalls and Caveats
The most important consideration is distinguishing between different magnesium formulations. Magnesium oxide, commonly used for constipation, is poorly absorbed and causes osmotic diarrhea, which could theoretically lead to dehydration and compensatory increased thirst/urination 1. However, magnesium glycinate does not have this effect.
What to Watch For
Gastrointestinal side effects are the primary concern with magnesium glycinate, not urinary symptoms. Common side effects include mild diarrhea, abdominal distension, and nausea, particularly at higher doses 1, 7.
Renal function must be assessed before supplementation. Patients with creatinine clearance <20 mL/min should avoid magnesium supplementation entirely due to risk of life-threatening hypermagnesemia 1, 7.
Liquid or dissolvable magnesium products are better tolerated than pills. If gastrointestinal side effects occur, switching formulations may help, but increased urination is not an expected side effect 1.
Clinical Bottom Line
If someone experiences increased urination after starting magnesium glycinate, look for alternative explanations. Consider whether they are drinking more fluids (common when starting supplements), taking other medications that affect urination, or experiencing unrelated medical conditions 8. The magnesium glycinate itself is not the likely culprit.
Recommended dosing starts at 320 mg/day for women and 420 mg/day for men (the RDA), with gradual increases as tolerated. At these doses, the primary effects are improved magnesium status and potential gastrointestinal symptoms, not increased urinary frequency 1, 7.