Magnesium glycinate, threonate, and citrate each serve different purposes, and choosing the wrong form means you either get side effects you do not need or miss the specific benefit you are after. Magnesium glycinate is best for sleep and anxiety, magnesium threonate targets cognitive function and brain fog, and magnesium citrate is most effective for constipation and general magnesium repletion.
Over 50% of adults in Western countries do not meet the recommended daily magnesium intake. But the supplement aisle offers a dozen forms, and most articles list them all without telling you which one to actually buy. Here is the direct comparison based on absorption data and clinical evidence.
Magnesium Glycinate: Best for Sleep and Anxiety
Magnesium glycinate binds magnesium to glycine, an amino acid that independently promotes relaxation and lowers core body temperature. This dual mechanism makes it the strongest option for sleep quality and anxiety reduction. Glycinate is highly bioavailable, gentle on digestion (no laxative effect), and does not compete with other minerals for absorption. Take 300 to 400mg in the evening, 30 to 60 minutes before bed. If you deal with perimenopause symptoms including insomnia and anxiety, glycinate is the form to start with.
Magnesium Threonate: Best for Brain Fog and Cognition
Magnesium L-threonate (branded as Magtein) is the only form clinically shown to cross the blood-brain barrier and increase brain magnesium concentrations. A 2024 study confirmed it improves sleep quality and daytime cognitive function in adults with self-reported sleep issues. Choose threonate if your primary concern is brain fog, memory, or cognitive decline rather than muscle relaxation or digestive regularity. The effective dose is 1,500 to 2,000mg of magnesium threonate (delivering 144mg elemental magnesium). It costs significantly more than glycinate, typically $30 to $50 per month versus $10 to $20.
Magnesium Citrate: Best for Constipation
Magnesium citrate has high bioavailability and a natural osmotic laxative effect that draws water into the intestines. This makes it ideal for constipation relief and general magnesium repletion, but unsuitable for bedtime use if loose stools are a concern. Standard dosing is 200 to 400mg daily. If you need both sleep support and digestive regularity, some practitioners recommend glycinate at night and a small dose of citrate in the morning.
| Form | Best For | Dose | Monthly Cost | GI Side Effects |
|---|---|---|---|---|
| Glycinate | Sleep, anxiety, muscle relaxation | 300-400mg before bed | $10-$20 | Minimal |
| L-Threonate | Brain fog, cognition, memory | 1,500-2,000mg daily | $30-$50 | Minimal |
| Citrate | Constipation, general repletion | 200-400mg daily | $8-$15 | Laxative effect |
Frequently Asked Questions
Can you take magnesium glycinate and threonate together?
Yes, they work through different pathways. Some people take glycinate at night for sleep and threonate in the morning for cognitive support. Track your total elemental magnesium intake to stay within the 300 to 420mg daily recommended range and avoid exceeding tolerable limits.
Which magnesium is best for perimenopause?
Magnesium glycinate is the best starting point for perimenopause because it addresses the most common complaints: insomnia, anxiety, and muscle tension. If brain fog is your primary symptom, add or switch to threonate. Ashwagandha paired with glycinate amplifies the cortisol-lowering effect.
Why does magnesium citrate cause diarrhea?
Magnesium citrate draws water into the intestines through osmosis. At higher doses this produces a laxative effect that can range from softer stools to full diarrhea. If you need magnesium for sleep or anxiety rather than bowel regularity, switch to glycinate or threonate to avoid this side effect entirely.
