One bad night of sleep can drive insulin sensitivity down by 25% — equivalent to six months of weight gain.
What sleep does to glucose
- Less than 6 hours: 50% higher diabetes risk (long-term studies)
- One bad night: 25–30% drop in insulin sensitivity
- Three nights of 4-hour sleep: glucose tolerance equal to a prediabetic
- Sleep apnea: independently raises HbA1c by ~0.5%
Why
Sleep deprivation raises cortisol, ghrelin (hunger hormone) and inflammatory markers. It lowers leptin (fullness hormone). Result: you're hungrier, crave sugar, and your cells resist insulin.
Practical fixes
- **Stop caffeine by 2 PM**. Half-life is 5–6 hours.
- **Cool your bedroom to 65–68°F**. Core temp must drop to fall asleep.
- **Block all light** with blackout curtains and a sleep mask.
- **No phone in bed** — blue light suppresses melatonin.
- **Walk for 10 minutes after dinner** — improves sleep onset.
- **Magnesium glycinate** 300–400mg, 1 hour before bed.
When to get screened for sleep apnea
- You snore loudly
- Partner reports you stop breathing during sleep
- You wake up with morning headaches
- You're sleepy during the day despite 7+ hours in bed
CPAP treatment for apnea can drop HbA1c 0.4% in 3 months.