When blood sugar drops too low, your body launches an emergency response to protect your brain. Because the brain runs almost entirely on glucose, even a modest dip below about 70 mg/dL triggers a cascade of hormonal signals designed to push blood sugar back up. What you feel during that process, and what happens if it fails, depends on how far your levels fall and how quickly your body responds.
Your Body’s Emergency Response
The moment blood sugar starts declining, the first thing your body does is cut insulin production. Insulin is what moves glucose out of your bloodstream and into cells, so dialing it back keeps more sugar circulating where it’s needed most.
If that isn’t enough, your pancreas releases glucagon, a hormone that tells the liver to break down its stored sugar and release it into the blood. At the same time, your adrenal glands pump out adrenaline, which works on multiple fronts: it signals the liver to produce new glucose, blocks insulin, reduces how much glucose your muscles absorb, and starts breaking down fat for energy. Adrenaline is also responsible for many of the physical symptoms you feel, like a racing heart and shaking hands.
Two slower-acting hormones, cortisol and growth hormone, kick in if the situation persists. Their job is to shift the rest of your body away from using glucose as fuel, essentially reserving whatever sugar is available for the brain. Cortisol activates fat burning and new glucose production, while growth hormone promotes fat breakdown and makes tissues less responsive to insulin.
What Low Blood Sugar Feels Like
Symptoms fall into two distinct categories, and recognizing which you’re experiencing helps you gauge how serious the episode is.
The first group comes from your nervous system reacting to adrenaline. These are the early warning signs: sweating, trembling, a pounding heartbeat, anxiety, and hunger. Your skin may feel clammy, and you might notice tingling around your lips or fingertips. These symptoms are uncomfortable but actually useful. They’re your body’s alarm system telling you to eat something.
The second group is more concerning. These symptoms come from your brain not getting enough fuel. They include difficulty concentrating, confusion, slurred speech, behavioral changes, blurred vision, headache, and fatigue. As blood sugar drops further, the consequences become severe: seizures, loss of consciousness, and in rare cases, death. At this stage, brain cells are literally running out of energy, and prolonged episodes can cause permanent neurological damage through cell death.
Low Blood Sugar While You Sleep
Nighttime episodes are particularly dangerous because you can’t recognize the warning signs while unconscious. According to Johns Hopkins Medicine, clues that low blood sugar occurred overnight include restless or irritable sleep, sweating or clammy skin, trembling, sudden changes in breathing patterns, nightmares, and a racing heartbeat. You might also wake up with a headache, feeling exhausted despite a full night’s rest, or with damp sheets from sweating.
A bed partner is often the first to notice. If they observe any of these signs regularly, it’s worth checking blood sugar levels during the night to confirm what’s happening.
When Warning Signs Stop Working
One of the most dangerous complications of repeated low blood sugar is losing the ability to feel it coming. This is called hypoglycemia unawareness, and it develops gradually. Each time you experience an episode, the blood sugar threshold that triggers warning symptoms drops a little lower. If symptoms started at 60 mg/dL yesterday, today they might not appear until 55 mg/dL.
The critical problem: while your symptom threshold keeps dropping, the level that causes you to pass out stays the same. This means the gap between “I feel something is wrong” and “I’m unconscious” keeps shrinking until, eventually, there’s no warning at all. People with diabetes who have frequent lows are most at risk for this pattern.
Who Gets Low Blood Sugar Without Diabetes
Low blood sugar isn’t exclusively a diabetes problem. In people without diabetes, it most commonly takes the form of reactive hypoglycemia, where blood sugar drops a few hours after eating. The exact cause often isn’t clear, but it tends to be connected to what and when a person eats, particularly meals heavy in refined carbohydrates.
Other triggers include alcohol consumption, which can interfere with the liver’s ability to release stored glucose. People who’ve had gastric bypass or other weight-loss surgery are also at higher risk because food moves through the digestive system faster than normal, causing an exaggerated insulin response. Rare causes include inherited metabolic conditions and certain types of tumors that produce excess insulin.
How to Treat an Episode
The standard approach is simple and known as the 15-15 rule: eat 15 grams of fast-acting carbohydrates, wait 15 minutes, then check your blood sugar again. Good sources of 15 grams include four glucose tablets, half a cup of juice or regular soda, or a tablespoon of honey. If your level is still low after 15 minutes, repeat the process.
Once blood sugar returns to a safe range, eating a small meal or snack with some protein and complex carbohydrates helps prevent another drop. Avoid over-treating with too much sugar, which can send your levels swinging in the other direction.
When Someone Can’t Treat Themselves
Severe episodes where a person is confused, seizing, or unconscious require outside help. The person cannot safely swallow food or liquid, so the treatment is glucagon, a hormone that rapidly signals the liver to dump sugar into the bloodstream.
Glucagon comes in two forms: a nasal spray and an injectable kit. The nasal version is dramatically easier for bystanders to use. In a simulation study, about 91% of both trained and untrained people successfully delivered the nasal spray in under 50 seconds. By comparison, only about 16% of trained users and none of the untrained users managed to correctly prepare and inject the injectable version. The injectable kit requires mixing a powder with liquid before injecting, a multi-step process that most people fumble under stress. If someone in your household is at risk for severe lows, having a nasal glucagon device on hand and making sure household members know where it is can be the difference between a scare and a crisis.
After a glucagon dose, the person typically regains consciousness within 10 to 15 minutes. They should eat as soon as they’re alert enough to swallow safely, since the glucagon effect is temporary and the liver’s sugar stores may already be depleted.