Low glucose, or hypoglycemia, means your blood sugar has dropped below 70 mg/dL. At that level, your body doesn’t have enough fuel to function normally, and you’ll likely start feeling symptoms like shaking, sweating, or sudden hunger. A reading below 54 mg/dL is considered severe and can cause confusion, difficulty speaking, or loss of consciousness.
Why Your Body Reacts So Strongly
Your brain runs almost entirely on glucose. When levels fall too low, your body treats it as an emergency and floods your system with adrenaline and noradrenaline to push sugar back into your bloodstream. That adrenaline surge is what causes many of the symptoms people notice first: a racing heart, trembling hands, sweating, and a wave of anxiety that seems to come from nowhere. These are your body’s alarm signals, not the direct effect of low sugar itself.
If glucose keeps dropping, the brain starts running short on fuel. That’s when a second set of symptoms appears: poor concentration, confusion, weakness, drowsiness, blurred vision, headache, dizziness, and slurred speech. These are more dangerous because they can make it harder to recognize what’s happening and take action.
Common Causes in People With Diabetes
If you take insulin or certain diabetes medications, low glucose is a familiar risk. It typically happens when your medication dose is too high relative to what you’ve eaten, when you skip or delay a meal, or when you exercise more than usual without adjusting your food intake. Alcohol can also lower blood sugar, especially if you drink without eating.
Some people with diabetes experience what’s called hypoglycemia unawareness, where repeated low episodes gradually train the body to stop sending those early warning signals like shaking and sweating. Without those alarms, blood sugar can drop dangerously low before the person realizes anything is wrong. This is one reason continuous glucose monitors have become valuable for people with frequent lows.
Low Glucose Without Diabetes
Low blood sugar in people without diabetes is less common, but it does happen. It generally falls into two categories based on timing.
Reactive hypoglycemia occurs within four hours of eating, usually after a high-carbohydrate meal. Your body overproduces insulin in response to the sugar load, which then drives blood glucose too low. People who are prediabetic or have had stomach surgery are more prone to this, because their bodies either misjudge insulin needs or absorb food too quickly into the small intestine.
Fasting hypoglycemia happens overnight or when too much time passes between meals. Several things can trigger it: binge drinking, serious illness affecting the liver, heart, or kidneys, or low levels of hormones like cortisol, thyroid hormone, or growth hormone. In rare cases, a tumor in the pancreas can produce excess insulin and drive blood sugar down repeatedly.
Certain medications can also lower blood sugar in people who don’t have diabetes. Beta-blockers, some heart rhythm drugs, certain antibiotics, anti-malaria drugs, and even high doses of aspirin have all been linked to drug-induced hypoglycemia.
Low Blood Sugar During Sleep
Nocturnal hypoglycemia is particularly tricky because you can’t feel the warning signs while asleep. Clues that it happened overnight include waking up with damp or clammy sheets, having nightmares, or feeling unusually tired and irritable in the morning despite a full night’s rest. A partner might notice restless sleep, trembling, or sudden changes in your breathing.
The risk goes up if you skip dinner, exercise heavily in the evening, or drink alcohol before bed. For people who experience this regularly, a doctor may recommend adjusting medication timing, setting an early morning alarm to check blood sugar, or using a continuous glucose monitor with a low-sugar alarm.
What to Do When Your Blood Sugar Drops
The standard approach is called the 15-15 rule: eat or drink 15 grams of fast-acting carbohydrates, then wait 15 minutes and check your blood sugar again. If it’s still below 70 mg/dL, repeat the process. Keep going until your levels return to a normal range. Good sources of 15 grams of carbs include four glucose tablets, half a cup of juice, or a tablespoon of honey. Once your blood sugar stabilizes, follow up with a balanced snack or small meal that includes both protein and carbs to keep it steady.
Severe episodes, where someone is too confused to eat or has lost consciousness, require help from another person. This is why people at risk for severe lows are often prescribed emergency glucagon kits that a bystander can administer.
Preventing Repeated Episodes
If you experience reactive hypoglycemia, dietary changes can make a significant difference. Eating smaller meals every three hours, choosing high-fiber foods like whole grains and vegetables over processed carbohydrates, and avoiding sugary foods on an empty stomach all help prevent the insulin overshoot that causes post-meal crashes. When you drink alcohol, eating something alongside it slows the effect on blood sugar.
For people with diabetes, prevention usually involves fine-tuning medication doses, eating consistently, and planning ahead for exercise. Keeping fast-acting carbs accessible at all times (in a bag, car, or nightstand) is a practical habit that can prevent a mild low from becoming a dangerous one.
If you’re getting frequent lows and don’t have an obvious explanation, the pattern itself is worth investigating. Recurring fasting hypoglycemia in someone without diabetes can point to hormonal deficiencies, liver problems, or rarely a pancreatic tumor, all of which are treatable once identified.