Insulin is a hormone primarily involved in blood sugar regulation, helping cells absorb glucose for energy or storage. It is produced by the pancreas and is crucial for managing conditions like diabetes, but it has no direct role in controlling sleep cycles. While blood sugar fluctuations can indirectly impact sleep quality — for instance, sharp spikes or drops in glucose can cause nighttime awakenings — insulin’s function is metabolic, not circadian. Confusing insulin with melatonin may arise from general awareness of how hormones affect health, but they operate in very different systems. Melatonin works with the brain’s sleep clock, while insulin works with the body’s energy balance. A poor night’s sleep can impair insulin sensitivity, and diabetes can affect sleep, but insulin doesn’t instruct the brain to sleep. That role belongs to melatonin, the master regulator of the sleep-wake rhythm.