Low blood sugar, called hypoglycemia, means your body doesn’t have enough glucose in your bloodstream to fuel your cells and brain. A blood sugar reading below 70 mg/dL is considered low, and anything below 54 mg/dL is classified as severely low. While most people associate this with diabetes, it can happen to anyone under the right circumstances.
What Happens Inside Your Body
Glucose is your brain’s primary fuel source. Unlike your muscles, which can burn fat for energy, your brain depends almost entirely on a steady supply of blood sugar to function. When levels start falling, your body launches a coordinated rescue effort: it dials back insulin production and releases a wave of hormones, including glucagon, adrenaline, cortisol, and growth hormone. These hormones work together to pull stored sugar out of your liver and push it back into your bloodstream.
Adrenaline is responsible for many of the symptoms you feel during a low. Your sympathetic nervous system, the same one that activates during a fight-or-flight response, triggers the release. That’s why a blood sugar drop can feel eerily similar to a panic attack, with a racing heart, shaking hands, and a sudden wave of anxiety. These sensations are actually your body’s alarm system working correctly, warning you to eat something before levels fall further.
Symptoms to Recognize
The symptoms of low blood sugar fall into two categories that tend to show up in sequence. The first wave comes from adrenaline and the nervous system: sweating, shakiness, a pounding heartbeat, hunger, and tingling around the lips or fingertips. You might feel anxious or irritable for no obvious reason. Your skin may feel warm and clammy.
If blood sugar continues to drop, a second set of symptoms emerges as your brain starts running short on fuel. These include confusion, difficulty concentrating, slurred speech, blurred or double vision, loss of coordination, and extreme fatigue. At very low levels, seizures or loss of consciousness can occur. In young children, these symptoms often overlap and are harder to identify, appearing as general behavioral changes rather than the classic pattern adults experience.
Why It Happens With Diabetes
The most common cause of hypoglycemia is diabetes treatment. Insulin and certain oral diabetes medications lower blood sugar by design, so if the dose is slightly too high, a meal is skipped, or physical activity burns through glucose faster than expected, levels can drop below the safe range. This is especially common overnight. Skipping dinner, exercising before bed, or drinking alcohol in the evening all increase the risk of blood sugar dipping while you sleep, when you’re unable to notice warning signs.
For people with diabetes who experience frequent lows, a dangerous pattern can develop called hypoglycemia unawareness. Normally, symptoms kick in around 60 mg/dL. But with repeated episodes, the threshold keeps shifting downward. Yesterday you felt shaky at 60; today you might not notice anything until you hit 55, then 50. The critical problem is that the blood sugar level triggering unconsciousness doesn’t shift along with it. The gap between “I feel fine” and “I’ve passed out” gets narrower and narrower, making severe episodes more likely without any warning.
Low Blood Sugar Without Diabetes
If you don’t have diabetes, low blood sugar is less common but still possible. The most frequently discussed form is reactive hypoglycemia, where blood sugar drops within a few hours after eating, typically after a meal heavy in refined carbohydrates. Your body overproduces insulin in response to the sugar spike, then overshoots on the way back down. The exact mechanism isn’t always clear, and doctors often focus on dietary adjustments rather than pinpointing a single cause.
Other triggers in people without diabetes include alcohol (which can block your liver’s ability to release stored glucose), prior stomach or bariatric surgery (which changes how quickly food hits the small intestine), inherited metabolic conditions, and rare insulin-producing tumors called insulinomas. Certain medications can also cause blood sugar to drop, including some beta-blockers used for blood pressure, specific antibiotics, heart rhythm medications, and some pain relievers.
When low blood sugar happens repeatedly in someone without diabetes and no obvious explanation, doctors may use a supervised fasting test. You fast under medical monitoring, sometimes for up to 72 hours, while blood sugar is checked at regular intervals. The test helps identify whether your body is producing too much insulin on its own, which can point toward a tumor or other treatable cause.
What Repeated Lows Do Over Time
A single mild episode of low blood sugar, while unpleasant, resolves quickly once you eat and doesn’t cause lasting harm. Repeated severe episodes are a different story. Prolonged hypoglycemia can injure the brain, disrupt heart rhythm, and is associated with increased mortality. In people with type 2 diabetes, severe hypoglycemia is one of the strongest predictors of major cardiovascular events and death, with studies showing the risk of dying is 1.7 to 4.3 times higher in those who experience one or more severe episodes.
The mechanisms behind this are becoming clearer. A severe blood sugar crash triggers a surge of inflammation, promotes blood clotting, damages the lining of blood vessels, and disrupts the electrical signaling in the heart. The adrenaline rush itself can lower potassium levels, which alters how the heart conducts electrical impulses and can set the stage for dangerous arrhythmias. These effects compound over time with repeated episodes, which is why preventing lows matters just as much as preventing highs for people managing diabetes.
Treating a Low in the Moment
The standard approach is the “15-15 rule.” Eat or drink about 15 grams of fast-acting carbohydrates: four glucose tablets, half a cup of juice or regular soda, or a tablespoon of honey. Wait 15 minutes, then recheck your blood sugar. If it’s still below 70, repeat. Once it normalizes, eat a small snack or meal with protein and complex carbs to keep it stable.
For severe episodes where someone is confused or unconscious, they cannot safely swallow food or liquid. Injectable glucagon, available as a kit or nasal spray, is the appropriate emergency treatment. This directly signals the liver to dump its glucose stores into the bloodstream.
Preventing Blood Sugar Drops
If you’re prone to lows, eating patterns matter more than any single food choice. Eating meals at consistent times, pairing carbohydrates with protein or fat to slow digestion, and avoiding long gaps between meals all help keep blood sugar steady. Alcohol on an empty stomach is one of the most reliable triggers for a drop, whether or not you have diabetes.
For overnight lows, a continuous glucose monitor that checks levels every five minutes and sounds an alarm when they start falling can be a significant safety net. Some people also benefit from a small bedtime snack that includes protein, adjusting the timing of evening medications, or setting an early-morning alarm to check levels and catch a pattern before it becomes dangerous.