Hypoglycemia is a condition where your blood sugar drops low enough to cause symptoms, generally below 70 mg/dL. It’s most common in people with diabetes, but it can also happen in people who don’t have diabetes. Understanding what triggers it, what it feels like, and how to respond quickly matters because untreated low blood sugar can become a medical emergency within minutes.
How Your Body Normally Handles Low Blood Sugar
Your body has a built-in system for keeping blood sugar stable. When glucose starts dipping into the low-normal range (around 80 to 85 mg/dL), your pancreas reduces insulin output so less sugar gets pulled from the bloodstream. If levels keep falling below about 65 to 70 mg/dL, a second line of defense kicks in: the pancreas releases glucagon, a hormone that signals the liver to break down its stored glycogen into glucose and release it into the blood. At the same time, your adrenal glands release adrenaline, which further stimulates the liver and kidneys to produce glucose while also limiting how much sugar your muscles and other tissues absorb.
The liver is the main organ responsible for pushing glucose back into circulation. Both the liver and kidneys have the specific enzyme needed to release glucose into the bloodstream, which is why they play such a central role. This whole cascade usually corrects a dip in blood sugar before you even notice it. When these defenses are weakened or overwhelmed, that’s when hypoglycemia becomes a problem.
Common Causes in People With Diabetes
For people managing diabetes with insulin or certain oral medications, hypoglycemia is an ongoing risk. The most common triggers are straightforward:
- Taking too much insulin relative to how much you’re eating or how active you are
- Not eating enough carbohydrates to match your insulin dose
- Mistiming insulin so it peaks when you don’t have enough food on board
- Physical activity, especially if it’s unplanned or happens close to bedtime, since exercise makes your cells absorb glucose more efficiently
- Alcohol, which interferes with the liver’s ability to release stored glucose, particularly dangerous when drinking at night
Some blood pressure medications called beta blockers can also contribute by masking early warning signs like a racing heart, making it harder to catch a low before it gets serious.
Low Blood Sugar Without Diabetes
Hypoglycemia in people without diabetes is less common but does happen. It falls into two categories based on timing.
Reactive hypoglycemia occurs after meals, typically within a few hours of eating. It can result from the pancreas overproducing insulin in response to a meal, sometimes due to enlarged or overactive insulin-producing cells. People who’ve had gastric bypass surgery are particularly susceptible because the altered digestive tract changes how quickly food is absorbed and how much insulin gets released in response.
Fasting hypoglycemia happens when blood sugar drops during periods without food. Causes include insulinomas (small tumors on the pancreas that produce excess insulin), certain cancers, liver disease, alcohol use, and some medications. Disorders affecting how the liver stores and releases glucose can also be responsible.
Doctors confirm non-diabetic hypoglycemia using a set of criteria known as Whipple’s Triad: a measured low blood glucose level, symptoms consistent with low blood sugar, and resolution of those symptoms once blood sugar returns to normal. All three must be present to confirm the diagnosis.
What Low Blood Sugar Feels Like
The symptoms of hypoglycemia come in two waves, reflecting how your body responds as glucose drops.
Early symptoms are driven by your body’s stress response as adrenaline floods the system. You may feel shaky, sweaty, anxious, or suddenly hungry. Your heart might pound or race. Some people notice tingling or numbness in their lips and fingertips. These warning signs are your body’s alarm system, and they’re the best window for catching and correcting a low.
If blood sugar continues to fall, the brain itself starts running short on fuel. This is when symptoms shift to confusion, difficulty concentrating, slurred speech, trouble walking, irritability, and unusual behavior that others might notice before you do. Severe episodes can cause seizures, loss of consciousness, and coma. Unlike many other conditions, these brain-related symptoms can appear rapidly, because the brain depends almost entirely on glucose for energy and has very limited reserves.
Hypoglycemia Unawareness
Some people with diabetes, especially those who’ve had the disease for many years or who maintain very tight blood sugar control, gradually lose the ability to feel early warning symptoms. This condition is called hypoglycemia unawareness, and it’s particularly dangerous because the first sign of a low may be confusion or loss of consciousness rather than the usual shakiness and sweating.
The underlying problem is a vicious cycle. Repeated episodes of low blood sugar cause the body to recalibrate its alarm threshold downward. The hormonal defense system, including glucagon, adrenaline, and growth hormone, becomes blunted after repeated lows. The brain adapts to functioning at lower glucose levels and stops triggering the stress response that produces noticeable symptoms. Each unrecognized episode reinforces the cycle, making future episodes both more likely and harder to detect.
Risk factors include intensive blood sugar management, a history of severe lows, long duration of diabetes, alcohol use, kidney problems, and frequent exercise. For people with this condition, continuous glucose monitors and automated insulin delivery systems (closed-loop systems) have been shown to reduce time spent in dangerously low ranges.
How to Treat a Low in the Moment
The standard approach is called the 15-15 rule. Eat or drink 15 grams of fast-acting carbohydrates, then wait 15 minutes and recheck your blood sugar. If it’s still below 70 mg/dL, repeat with another 15 grams. Keep cycling through this process until your levels return to your target range. Good sources of 15 grams of fast-acting carbs include four glucose tablets, four ounces of juice, or a tablespoon of sugar dissolved in water.
For severe episodes where someone is unconscious or unable to swallow safely, oral carbohydrates aren’t an option because of the choking risk. This is where glucagon comes in. Glucagon is a prescription emergency medication available in several forms: a traditional injection kit that requires mixing a powder with sterile water, a pre-filled auto-injector designed for thigh injection (similar to an EpiPen), and a nasal spray that delivers medication through a single nostril. Any of these can be administered by a family member, coworker, or bystander without medical training. If someone is unconscious, they should be rolled onto their side to prevent choking, and emergency services should be called.
Long-Term Risks of Repeated Lows
A single mild episode of hypoglycemia, caught and treated quickly, isn’t likely to cause lasting harm. But repeated or severe episodes carry real consequences. When the brain is deprived of glucose, it’s also deprived of adequate oxygen. Research links frequent significant drops in blood sugar to problems with memory, attention, and depression over time. Severe episodes involving seizures or loss of consciousness pose immediate physical dangers from falls and accidents, on top of the neurological risks.
For people with diabetes, fear of hypoglycemia can also become a barrier to good blood sugar management. Some people intentionally keep their blood sugar higher than recommended to avoid lows, which increases the risk of long-term complications from high blood sugar instead. Finding the balance between preventing highs and avoiding dangerous lows is one of the central challenges of diabetes care.