Diabetes doesn’t just raise your blood sugar. It can seriously disrupt your sleep. Sleep difficulties affect roughly two-thirds of people with type 2 diabetes, and the relationship runs both directions: diabetes disrupts sleep, and poor sleep makes diabetes harder to control. This creates a cycle that can be difficult to break without addressing both problems at once.
How Common Sleep Problems Are in Diabetes
About 32% of people with type 2 diabetes have measurably poor sleep quality, and the real number is likely higher since many sleep issues go unrecognized. In one large study, 21.1% of diabetic patients reported regular trouble falling asleep, 21.9% had trouble staying asleep, and 12.2% experienced excessive daytime sleepiness. These aren’t minor inconveniences. Chronic sleep disruption worsens blood sugar control, which in turn makes sleep even harder to come by.
Why High Blood Sugar Wakes You Up at Night
When blood sugar runs high, your kidneys work overtime to filter the excess glucose out through urine. This leads to increased urine production, sometimes exceeding 2,800 mL in a 24-hour period. At night, that means your bladder fills faster than it normally would, waking you up to use the bathroom. Waking two or more times per night to urinate (a threshold doctors consider clinically significant) fragments your sleep in ways that prevent you from cycling through the deeper, more restorative stages.
Blood sugar fluctuations themselves also trigger awakenings. Overnight, blood sugar in a healthy person hovers around 5.0 mmol/L (90 mg/dL). When it swings above or below that range, your brain notices. Drops below about 3.8 mmol/L (68 mg/dL) activate your body’s emergency counterregulatory systems, and drops below 3.0 mmol/L (54 mg/dL) can produce full-blown symptoms: sweating, trembling, a racing heartbeat, nightmares, and restless sleep. Some people sleep right through these episodes without waking, which is its own concern, but many are jolted awake by the adrenaline surge their body mounts in response.
Nerve Pain That Gets Worse at Bedtime
Diabetic peripheral neuropathy, the nerve damage that causes tingling, burning, or shooting pain in the feet and hands, is one of the most direct paths from diabetes to insomnia. The pain tends to worsen at night, partly because there are fewer distractions and partly because lying down changes blood flow to the extremities. More severe pain consistently correlates with worse sleep quality. For people dealing with neuropathy, falling asleep can take much longer, and staying asleep becomes unreliable.
Sleep Apnea: The Hidden Overlap
Obstructive sleep apnea is strikingly common in people with type 2 diabetes, yet most cases go undiagnosed. One primary care study found that only 18% of diabetic patients had been diagnosed with sleep apnea, far below the 87% prevalence that screening tools predicted. The overlap exists because obesity drives both conditions, but the relationship goes deeper than shared weight.
When sleep apnea causes repeated pauses in breathing, blood oxygen drops. Those low-oxygen episodes decrease insulin sensitivity and trigger the release of stress hormones that raise blood sugar. The body also produces more inflammatory signals and becomes resistant to leptin, a hormone that regulates appetite and is linked to insulin function. So sleep apnea doesn’t just coexist with diabetes. It actively makes it worse, while diabetes simultaneously increases the risk of developing sleep apnea.
If you snore loudly, feel exhausted despite a full night’s sleep, or your partner has noticed you stop breathing during the night, it’s worth getting screened. The American Diabetes Association now recommends sleep health screening for people with diabetes and those at risk for it.
Restless Legs and Diabetes
Restless leg syndrome, that irresistible urge to move your legs when you’re lying still, also shows up more frequently in people with diabetes. The connection likely involves nerve damage similar to what causes peripheral neuropathy. Iron plays a role too, since the brain needs iron to produce dopamine, a chemical involved in movement control. Interestingly, in people with diabetes, restless leg syndrome appears to occur independently of iron levels, suggesting that the nerve damage itself may be the primary driver.
The Stress Hormone Feedback Loop
Sleep deprivation raises cortisol, your body’s main stress hormone. In one study, six consecutive nights of sleeping only four hours increased evening cortisol levels, ramped up the sympathetic nervous system (your fight-or-flight response), and decreased the body’s ability to handle glucose by about 30%. That degree of impairment mimics what you’d see in early type 2 diabetes.
The problem compounds over time. Higher cortisol impairs insulin function, which raises blood sugar, which disrupts sleep through the mechanisms described above, which raises cortisol further. This is the “vicious circle” that researchers describe when they talk about the bidirectional relationship between sleep and diabetes. Breaking the cycle usually requires tackling both blood sugar management and sleep habits simultaneously rather than treating one and hoping the other resolves on its own.
Metformin and Sleep
One often-overlooked contributor is metformin itself, the most commonly prescribed diabetes medication worldwide. About 1.4% of people taking metformin report insomnia as a side effect, and nightmares have also been documented. This side effect appears more frequently in older patients, those with obesity, and people who are newly diagnosed and just starting the medication. No other class of diabetes drug has this particular association. If your sleep problems started around the same time you began metformin, or if you’ve noticed vivid or disturbing dreams, it’s worth raising with whoever manages your diabetes care.
Keeping Blood Sugar Stable Overnight
The single most effective thing you can do to protect your sleep is minimize blood sugar swings between bedtime and morning. In healthy adults, blood sugar overnight stays close to 5.0 mmol/L (90 mg/dL). Large meals close to bedtime, especially those high in refined carbohydrates, can push blood sugar up and then cause a reactive dip hours later, both of which can wake you.
Consistent meal timing matters more than most people realize. Your body’s glucose regulation is tightly linked to your circadian rhythm. Eating at irregular times, or eating large amounts late at night, disrupts the hormonal systems that keep blood sugar steady while you sleep. A lighter evening meal, finished two to three hours before bed, gives your body time to bring glucose levels back toward baseline before you lie down.
Monitoring overnight patterns with a continuous glucose monitor, if you have access to one, can reveal whether your nighttime awakenings correspond to blood sugar spikes or dips. That information makes it much easier to adjust meals, medication timing, or both.