Is magnesium glycinate better than magnesium citrate?

For sleep and muscle function, yes — glycinate is better tolerated and does not cause the laxative effect. For constipation, citrate is the better choice because that laxative effect is the goal. Both are well absorbed.

Can I take magnesium with levothyroxine?

Not at the same time. Magnesium chelates levothyroxine and reduces its absorption, so leave at least four hours between the two. Take levothyroxine on an empty stomach first thing.

What is the best time to take magnesium glycinate?

Evening, 1-2 hours before bed. Magnesium supports parasympathetic tone and the glycine contributes a mild calming effect, so evening dosing aligns with its physiological role.

How much magnesium is too much?

The upper intake level for supplemental magnesium is 350 mg per day for adults. Doses above this are not toxic in healthy kidneys, but they reliably cause loose stools. The UL does not apply to magnesium from food.

Should I take magnesium with vitamin B6?

It helps. Vitamin B6 as pyridoxal-5-phosphate increases cellular magnesium retention, so the combination raises intracellular magnesium more than magnesium alone.

Magnesium Glycinate: Dose, Timing and Interactions

Key points

Delivers 14% elemental magnesium by weight, so 200 mg glycinate yields roughly 28 mg elemental — check the label for the elemental figure.
Glycine is itself calming, which is why this form is popular for sleep.
Take with vitamin B6, which improves cellular magnesium retention.

What magnesium actually does

Magnesium is a cofactor in more than 300 enzymatic reactions. It is required for ATP to be biologically active, which is why deficiency shows up first as fatigue, muscle cramping and poor sleep rather than as a single dramatic symptom.

It also acts as a physiological calcium channel blocker. That is the mechanism behind its calming effect and its role in blood pressure regulation.

Why the glycinate form

Magnesium oxide is cheap but poorly absorbed, roughly 4% bioavailable, and draws water into the intestine. Magnesium citrate is better absorbed but still laxative at higher doses. The bisglycinate chelate binds magnesium to two glycine molecules, which shields it from phytates and allows absorption through dipeptide pathways rather than relying solely on the saturable ion channel.

For most people targeting sleep or muscle function, glycinate is the form that reaches the bloodstream without gastrointestinal price.

Timing and interactions

Take magnesium in the evening, one to two hours before bed. Absorption is not strongly food-dependent, so an empty stomach is fine if it does not cause upset.

Two interactions matter. First, magnesium salts chelate levothyroxine and reduce thyroid hormone absorption — keep four hours between them. Second, magnesium binds fluoroquinolone and tetracycline antibiotics, reducing antibiotic absorption by up to 60%, so separate by two hours before or six hours after the antibiotic dose.

Alcohol increases renal magnesium loss and adds to sedation. Do not take magnesium with alcohol.

How much

The RDA is 420 mg daily for adult men and 320 mg for women, but that figure includes food. The tolerable upper intake level for supplemental magnesium is 350 mg per day, set on the basis of diarrhea rather than toxicity. Most people do well on 200-400 mg of elemental magnesium from supplements, with the balance coming from diet.