Magnesium for Sleep — Which Forms Actually Work?

Why does magnesium improve sleep?

Magnesium is a cofactor for over 300 enzymes and plays a key role in regulating neurotransmitters associated with relaxation and sleep:

• GABA — magnesium activates GABA-A receptors, producing calming effects
• Melatonin regulation — magnesium deficiency is associated with low melatonin levels
• Cortisol reduction — magnesium inhibits the HPA stress axis, making it easier to fall asleep

Form comparison

Magnesium bisglycinate (best choice)

• Absorption: ~40%
• No gut stimulation
• Glycine itself is calming and improves sleep
• Dose for sleep: 200–400mg elemental magnesium, 1h before bed

Magnesium L-threonate (premium, brain)

• Crosses the blood-brain barrier
• MIT studies show improved synaptic density and memory function
• More expensive, slower to build levels

Magnesium citrate (budget compromise)

• ~25% absorption, inexpensive
• Can cause gut loosening at higher doses