Your cortisol spike at 3 a.m. is not insomnia. It is blood sugar.

During sleep, your brain relies almost entirely on glucose for fuel. The liver maintains blood sugar through a process called glycogenolysis, breaking down stored glycogen and releasing glucose into the bloodstream. If liver glycogen is low, or if insulin sensitivity is poor, blood glucose can drop to a level that the hypothalamus perceives as threatening.

The hypothalamus does not negotiate. It triggers the sympathetic nervous system and the HPA axis, releasing cortisol and adrenaline. These hormones stimulate gluconeogenesis, breaking down protein and fat to make new glucose. They also raise heart rate, blood pressure, and mental alertness. From an evolutionary perspective, this is a brilliant survival mechanism. From the perspective of someone trying to sleep through the night, it is a disaster.

The irony is that this often happens in people who eat a high carbohydrate dinner or snack before bed. A large carb load spikes insulin, which drives glucose into cells and suppresses liver glucose output. As the meal digests and insulin remains elevated, blood sugar falls below the baseline. The bigger the spike, the harder the fall, and the more likely the hypothalamic alarm fires in the early morning hours.

Nocturnal hypoglycemia is not rare. It is underdiagnosed because most people do not measure blood sugar at 3 a.m. If you wear a continuous glucose monitor, you will often see a dip into the 60s or low 70s right before a wake up event, followed by a sharp rise as cortisol and adrenaline kick in. The rise is the rescue. The wake up is the cost.

The pattern is most common in people with poor insulin sensitivity, including those with prediabetes, metabolic syndrome, polycystic ovary syndrome, and chronic stress. It is also common in people who undereat during the day and then overeat at night, creating a volatile glucose curve. Women in the luteal phase of their menstrual cycle are more susceptible due to progesterone induced insulin resistance.

Paradoxically, it is also common in very low carbohydrate dieters and intermittent fasters who have not fully adapted to fat burning. The brain can use ketones for some of its energy, but not all of it. If ketone production is insufficient and liver glycogen is depleted, the same alarm fires. The fix is rarely to add more carbs. It is usually to stabilize the glucose curve with better macronutrient balance.

The simplest intervention is to change what you eat for dinner, not how much. Reduce refined carbohydrates and added sugar. Add protein and fat, both of which slow gastric emptying and blunt the insulin response to any carbs you do eat. A dinner of salmon, vegetables, and olive oil produces a far flatter glucose curve than pasta with tomato sauce and garlic bread.

If you need a bedtime snack, make it protein and fat, not carbs. A small handful of nuts, a piece of cheese, or a few spoonfuls of Greek yogurt provide sustained energy without the insulin spike. The goal is to give the liver something to work with during the night so it does not run out of fuel and trigger the alarm.

Some people benefit from a small amount of raw honey before bed, a trick popularized by Dave Asprey and others. The logic is that honey provides a quick glucose hit that signals the liver to reduce insulin output and maintain glycogenolysis. The evidence for this is anecdotal and mechanistically speculative, but some people swear by it. I would try the protein and fat approach first.

Cortisol has a natural daily rhythm. It is lowest around midnight and begins a slow rise starting at 3 to 4 a.m. to prepare the body for waking. This normal early morning cortisol rise is gentle and usually does not wake you. But if your baseline cortisol is already elevated from chronic stress, or if your circadian rhythm is disrupted from shift work, travel, or blue light exposure, the nocturnal rise can become steep enough to trigger awakening.

This means that even if your blood sugar is technically stable, high baseline cortisol can lower the threshold for a wake up event. Stress and poor sleep hygiene do matter. They are just not the whole story. In most cases, the metabolic instability comes first, and the cortisol sensitivity makes it worse.

The fix is twofold. Stabilize the blood sugar with dinner composition. And lower the baseline cortisol with consistent sleep and wake times, morning sunlight, moderate exercise, and stress management during the day. Doing only one of these is like bailing water with a bucket that has a hole in it.

Not every 3 a.m. wake up is metabolic. Obstructive sleep apnea causes frequent nocturnal awakenings, often with a racing heart, and is commonly misdiagnosed as anxiety. The difference is that apnea related wake ups happen throughout the night, not just at 3 a.m., and are often accompanied by gasping or snoring. If you suspect this, get a sleep study.

Hyperthyroidism can cause nocturnal palpitations and insomnia. GERD can wake you with acid reflux. Nocturia from prostate issues or diabetes can force bathroom trips. Menopausal hot flashes are notorious for 3 a.m. disruptions. And true generalized anxiety disorder can produce early morning awakening with dread and rumination.

The key diagnostic clue is the pattern. If you wake up at roughly the same time every night, heart pounding, sometimes hungry, and you fall back asleep after an hour, it is almost certainly blood sugar. If the wake ups are random, accompanied by other symptoms, or do not fit the metabolic pattern, see a clinician.

Here is what I suggest, based on the literature and what I have seen work. For one week, eat dinner at least three hours before bed. Make it high in protein and fat, low in refined carbohydrate. Do not drink alcohol within three hours of sleep. If you need a snack before bed, have protein and fat. Set a consistent sleep and wake time, even on weekends. Get 10 minutes of morning sunlight within an hour of waking.

If you have access to a continuous glucose monitor, wear it for two weeks and look for dips below 70 milligrams per deciliter between midnight and 4 a.m. Correlate those dips with wake up events. The pattern is usually obvious within a few days.

If you do all of this and still wake up at 3 a.m., then it is time to dig deeper. Test thyroid function, consider a sleep study, evaluate for depression or anxiety, and work with a clinician who understands that sleep is a system, not a switch.