Yes, hypoglycemia is the medical term for low blood sugar. It’s generally defined as a blood glucose level below 70 mg/dL, though symptoms can appear at different thresholds depending on the person. Hypoglycemia is most common in people with diabetes, but it can also affect people without it.
What Counts as Low Blood Sugar
Blood sugar (glucose) is the body’s primary fuel, especially for the brain. A normal fasting blood sugar falls between roughly 70 and 100 mg/dL. When it drops below 70 mg/dL, it’s considered low. Some people start feeling symptoms in the mid-70s, while others don’t notice anything until they’re well into the 50s or lower.
For people without diabetes, doctors typically confirm hypoglycemia using a set of three criteria known as Whipple’s triad: you have symptoms consistent with low blood sugar, a lab test shows your glucose is genuinely low at the time of those symptoms, and the symptoms go away once your blood sugar comes back up. All three need to be present. This matters because many symptoms of hypoglycemia overlap with anxiety, hunger, or fatigue, and a one-time low reading on a home glucose meter isn’t enough to diagnose a true hypoglycemic disorder.
How Your Body Responds to Dropping Glucose
Your body has a built-in alarm system for falling blood sugar. When glucose starts to drop, your pancreas releases glucagon, a hormone that signals the liver to dump stored sugar into the bloodstream. At the same time, your adrenal glands release adrenaline (the “fight or flight” hormone), along with cortisol and growth hormone. Together, these hormones work to push blood sugar back up.
The adrenaline surge is what produces many of the early warning symptoms people feel: shakiness, a racing heart, sweating, and sudden hunger. These are your body’s way of alerting you that fuel is running low. If blood sugar keeps falling despite this hormonal response, the brain starts running short on energy, which causes a second, more dangerous set of symptoms.
Symptoms to Recognize
Early signs of low blood sugar tend to come on quickly and include:
- Shakiness or trembling
- Sweating, sometimes with pale skin
- Fast or irregular heartbeat
- Dizziness
- Sudden hunger or nausea
- Tingling or numbness in the lips, tongue, or cheek
- Trouble concentrating
If blood sugar continues to fall, the brain’s energy supply gets compromised. At that point, symptoms shift to confusion, unusual behavior, clumsiness, muscle weakness, and drowsiness. Severe hypoglycemia can cause seizures, convulsions, loss of consciousness, or coma. The brain needs a steady supply of glucose to function, so prolonged severe lows are a medical emergency.
Nighttime Symptoms
Low blood sugar can also happen during sleep, which makes it harder to catch. Signs of nocturnal hypoglycemia include damp sheets from sweating, restless or irritable sleep, nightmares, sudden changes in breathing patterns, and waking up feeling confused, tired, or unusually irritable. A partner may notice trembling or a racing heartbeat before you do.
What Causes Low Blood Sugar
In people with diabetes, the most common cause is too much insulin or certain oral diabetes medications relative to how much food was eaten or how much physical activity was done. Skipping meals, eating less than usual, exercising harder than expected, or drinking alcohol on an empty stomach can all tip the balance.
Several categories of medication carry hypoglycemia risk. Insulin is the most obvious, but sulfonylureas (a class of pills that stimulate the pancreas to make more insulin) are a frequent culprit. Certain heart rhythm medications, some antibiotics, and even common pain relievers can lower blood sugar in susceptible people.
In people without diabetes, hypoglycemia is less common but does occur. Potential causes include insulin-producing tumors of the pancreas, adrenal gland disorders that reduce cortisol production, severe liver or kidney disease, prolonged fasting, heavy alcohol use, and certain rare enzyme deficiencies. Reactive hypoglycemia, where blood sugar drops a few hours after eating (often after a high-carbohydrate meal), is another pattern some people experience.
The 15-15 Rule for Treatment
The standard approach for treating a mild to moderate low is simple: eat 15 grams of fast-acting carbohydrates, then wait 15 minutes. Good options include four glucose tablets, half a cup of fruit juice, half a can of regular soda, or a tablespoon of honey or sugar. After 15 minutes, check your blood sugar again. If it’s still below 70 mg/dL, repeat the process.
Once blood sugar returns to a safe range, eating a small snack or meal that includes protein and complex carbohydrates (like crackers with cheese or a sandwich) helps keep it stable. Fast-acting sugar gets glucose up quickly, but it also burns through quickly, so that follow-up food prevents another drop.
For severe episodes where someone is unconscious or unable to swallow safely, emergency glucagon is the appropriate intervention. Glucagon comes in injectable and nasal spray forms and works by triggering the liver to release stored sugar. Once the person regains consciousness and can swallow, they should consume a fast-acting sugar source followed by a more substantial snack, and emergency medical help should be called.
Hypoglycemia Unawareness
About 25% of people with type 1 diabetes develop a condition called hypoglycemia unawareness, where the body’s normal warning signals (the shaking, sweating, and racing heart) become muted or disappear entirely. This typically happens after repeated episodes of low blood sugar, which essentially trains the body to stop sounding the alarm.
Someone with hypoglycemia unawareness might not realize their blood sugar is low until it’s already in the 50s or lower, at which point cognitive symptoms like confusion are already setting in. The main danger is losing consciousness without warning, which can lead to falls, car accidents, or injuries at work. Frequent blood sugar monitoring or a continuous glucose monitor is especially important for people in this situation, because they can’t rely on physical symptoms to alert them.
When Hypoglycemia Is Reactive vs. Fasting
Doctors generally distinguish between two patterns of hypoglycemia in people without diabetes. Reactive hypoglycemia happens within two to four hours after eating, particularly after meals heavy in refined carbohydrates. The body overshoots its insulin response, driving blood sugar too low. This type is more common and usually manageable through dietary changes like eating smaller meals, pairing carbohydrates with protein and fat, and avoiding sugary drinks on an empty stomach.
Fasting hypoglycemia occurs when blood sugar drops during periods without food, such as overnight or between meals. This pattern is more likely to point to an underlying medical condition like an insulin-producing tumor, a hormonal deficiency, or organ disease. It generally requires medical investigation to identify and treat the root cause, rather than just managing symptoms with dietary adjustments.