Blood sugar drops below 70 mg/dL when your body either produces too much insulin, doesn’t release enough stored glucose, or burns through glucose faster than it can be replaced. This condition, called hypoglycemia, has a wide range of triggers, from medications and missed meals to alcohol and intense exercise. Some causes are straightforward lifestyle factors you can adjust, while others point to underlying medical conditions worth investigating.
How Your Body Normally Regulates Blood Sugar
Your blood sugar stays stable through a constant balancing act between insulin and several counter-regulatory hormones. After you eat, your pancreas releases insulin to move glucose from your blood into your cells for energy. Between meals, your liver steps in by converting its stored glycogen back into glucose and releasing it into your bloodstream. Hormones like glucagon, cortisol, and adrenaline all play supporting roles in keeping glucose from falling too low.
A blood sugar drop happens when one or more parts of this system overperform or underperform. Too much insulin pushes glucose out of the blood too aggressively. A liver that can’t release stored glucose leaves you running on empty. Understanding which part of the system is disrupted helps explain why your blood sugar is falling.
Diabetes Medications
The most common cause of low blood sugar is medication used to manage diabetes. A class of oral drugs called sulfonylureas works by stimulating the pancreas to release more insulin, targeting specific receptors on the insulin-producing cells. The problem is that these drugs don’t adjust based on how much glucose is actually in your blood. They keep pushing insulin out even when your levels are already adequate, which can tip you into a low.
Insulin injections carry a similar risk. Taking too much insulin, timing a dose poorly relative to a meal, or injecting insulin and then eating less than planned can all drive blood sugar down. If you take insulin or sulfonylureas and skip a meal, delay eating, or eat fewer carbohydrates than usual, the mismatch between medication and food intake is often enough to cause a drop.
Skipping or Delaying Meals
Even without diabetes medications, going too long without eating can lower blood sugar. Your liver stores enough glycogen to maintain blood glucose for several hours, but those reserves are finite. Once they’re depleted, your body relies on making new glucose from proteins and fats, a slower process that may not keep pace with demand. People who skip breakfast, fast without preparation, or eat irregularly are more likely to experience dips, especially if they’re also physically active.
Alcohol and the Liver
Alcohol is one of the more underappreciated causes of low blood sugar. Your liver is responsible for releasing stored glucose between meals, but when it’s busy processing alcohol, that glucose-releasing function gets suppressed. Specifically, alcohol changes the chemical environment inside liver cells in a way that blocks the conversion of stored energy into glucose. It also interferes with the signaling pathways that normally activate glucose production.
This means drinking on an empty stomach, or drinking heavily without eating, can cause a significant blood sugar drop. The effect can be delayed, too. Your blood sugar might not fall until hours after your last drink, when you’re asleep and unlikely to notice symptoms. This makes alcohol-related hypoglycemia particularly dangerous, because it can be mistaken for intoxication by the people around you.
Exercise and Physical Activity
Physical activity pulls glucose out of your blood and into your muscles for fuel through both insulin-dependent and insulin-independent pathways. During moderate to intense exercise, your muscles absorb glucose at a much higher rate than at rest. If you haven’t eaten enough beforehand or if you’re taking insulin, this increased demand can outstrip supply and cause a drop.
What surprises many people is that the risk doesn’t end when the workout does. After exercise, your body works to replenish the glycogen stores in your muscles, which means glucose continues to be pulled from the bloodstream for hours. Research shows the risk of a post-exercise low peaks about one hour after activity and then again five to ten hours later. That second window is why people with diabetes sometimes experience low blood sugar in the middle of the night after an active day. The elevated risk can persist for up to 24 hours after a workout.
Reactive Hypoglycemia After Meals
Some people experience blood sugar drops within four hours of eating, a pattern called reactive hypoglycemia. This typically happens when the body overshoots its insulin response to a meal, releasing more insulin than needed and driving blood sugar below normal levels. Meals high in refined carbohydrates and sugar tend to trigger the sharpest insulin spikes, making this overcorrection more likely.
In people without diabetes, the exact cause of reactive hypoglycemia often isn’t fully understood. It may relate to individual differences in how quickly food is digested and how sensitive the pancreas is to rising glucose. People who’ve had gastric bypass or other bariatric surgery are at higher risk because food moves into the small intestine much faster after these procedures, triggering a rapid and exaggerated insulin release. Rare inherited metabolic conditions and certain pancreatic tumors can also cause post-meal drops.
Underlying Medical Conditions
Several medical conditions can cause blood sugar to drop independently of meals or medications. An insulinoma is a tumor in the pancreas that produces insulin continuously, regardless of whether blood sugar is high or low. Normally, your pancreas stops releasing insulin when glucose levels fall. An insulinoma overrides that safety mechanism, keeping insulin flowing and driving blood sugar dangerously low. Symptoms are most common during fasting or when meals are skipped. People with certain genetic conditions, such as multiple endocrine neoplasia type I, face a higher risk of developing these tumors.
Adrenal insufficiency is another potential cause. Your adrenal glands produce cortisol, which helps maintain blood sugar between meals by signaling the liver to release glucose. When cortisol production is inadequate, that signal weakens, and blood sugar can fall. Severe liver disease and kidney disease can also impair glucose regulation, since both organs play roles in producing and recycling glucose.
Early Versus Late Warning Signs
Your body sends two waves of symptoms as blood sugar drops, and recognizing both matters. The first wave comes from your nervous system’s stress response: sweating, a racing heart, trembling, anxiety, and sudden hunger. These symptoms typically appear first and serve as an early alarm system.
If blood sugar continues to fall, the second wave hits. This one reflects your brain running low on fuel: confusion, difficulty concentrating, irritability, slurred speech, and in severe cases, loss of consciousness or seizures. The transition from the first set of symptoms to the second can happen quickly, which is why acting on the early signs is important.
When Your Body Stops Warning You
People who experience frequent episodes of low blood sugar can develop a condition called hypoglycemia unawareness. With repeated lows, the glucose level that triggers warning symptoms keeps shifting downward. If your body sent alarm signals at 60 mg/dL yesterday, it might not react until 55 mg/dL today. Over time, you lose the early-warning sweating and shaking entirely, and the first sign of a low may be confusion or disorientation, symptoms that make it harder to help yourself.
This creates a dangerous cycle: frequent lows cause unawareness, and unawareness leads to more severe lows. Researchers are still investigating whether this represents the brain adapting to lower glucose levels or whether it’s connected to a loss of glucagon response. Avoiding lows for a period of several weeks can often restore some degree of symptom awareness.
How to Treat a Low in the Moment
The standard approach for a mild drop is the 15-15 rule: eat 15 grams of fast-acting carbohydrate and wait 15 minutes. Good options include four glucose tablets, four ounces of juice or regular soda, or a tablespoon of honey. After 15 minutes, check your blood sugar again. If it’s still below 70 mg/dL, repeat with another 15 grams. Once your levels stabilize, eating a small meal or snack with protein and complex carbohydrates helps prevent another dip.
Severe episodes, where a person is unconscious or unable to swallow safely, require help from someone else. Injectable glucagon kits and nasal glucagon sprays are designed for these situations and can be used by a family member or bystander to raise blood sugar quickly.