When your blood sugar drops below about 70 mg/dL, your body doesn’t have enough glucose to fuel your brain and muscles normally. This is called hypoglycemia, and it can cause symptoms ranging from shakiness and sweating to confusion and loss of consciousness. It happens most often in people with diabetes who take insulin or certain medications, but it can also occur in people without diabetes.
What Happens Inside Your Body
Your body has a built-in alarm system for low blood sugar. Specialized glucose sensors scattered throughout your body detect the drop and trigger a cascade of hormones to push your levels back up. Your pancreas releases glucagon, which tells your liver to dump stored sugar into your bloodstream. At the same time, your adrenal glands release adrenaline, which does double duty: it signals your liver to produce even more glucose while also dialing back insulin production.
Cortisol and growth hormone kick in too, both working to raise blood sugar over a longer timeframe. That surge of adrenaline is also responsible for many of the physical symptoms you feel, like a racing heart, sweating, and trembling. These sensations are uncomfortable, but they serve a purpose: they’re your body’s way of telling you to eat something, fast.
How Low Blood Sugar Feels
The earliest symptoms tend to be physical and hard to ignore. You may notice shakiness, sweating, sudden hunger, a fast or irregular heartbeat, dizziness, or tingling in your lips or tongue. You might look pale. These signs typically appear first because they’re driven by that adrenaline surge.
If your blood sugar keeps falling, the symptoms shift from physical to cognitive. Your brain is the organ most sensitive to glucose deprivation, and when it doesn’t get enough, you may experience difficulty concentrating, irritability, confusion, slurred speech, or loss of coordination. Some people describe it as feeling “foggy” or acting unlike themselves. At very low levels (below 54 mg/dL), you can lose consciousness or have a seizure.
What Causes It
In People With Diabetes
The most common cause is a mismatch between medication and your body’s needs. Taking too much insulin, skipping a meal after taking medication, exercising more than usual, or drinking alcohol can all drive blood sugar lower than expected. The longer someone has had diabetes, the more likely they are to experience episodes, especially if they’ve been managing their blood sugar very aggressively with tight targets.
In People Without Diabetes
Low blood sugar without diabetes is less common, and the cause is often harder to pin down. One pattern, called reactive hypoglycemia, happens a few hours after eating, particularly after meals high in refined carbohydrates. Your body overshoots its insulin response, and blood sugar dips too low. Alcohol, previous stomach or bariatric surgery, inherited metabolic conditions, and rarely certain tumors can also cause it.
How It’s Classified
Doctors group low blood sugar into levels based on severity. Level 1 hypoglycemia means your reading falls between 54 and 69 mg/dL. You’ll likely feel symptoms, but you can treat it yourself. Level 2 is anything below 54 mg/dL, which is considered clinically significant and requires immediate attention. Severe hypoglycemia, sometimes called Level 3, is defined not by a specific number but by the fact that you need someone else’s help to recover, whether that means a family member giving you glucose or a paramedic responding to a call.
What to Do When It Happens
The standard approach is called the 15-15 rule: eat 15 grams of fast-acting carbohydrate and wait 15 minutes. Good options include four glucose tablets, half a cup of juice or regular soda, or a tablespoon of honey. After 15 minutes, check your blood sugar again if possible. If you still don’t feel better or your reading is still low, repeat with another 15 grams.
If someone is too confused to eat safely, feels like they might pass out, or loses consciousness, they need glucagon, a hormone that rapidly raises blood sugar. Glucagon comes in injectable and nasal spray forms, and people at risk for severe episodes should keep one accessible. If glucagon isn’t available and the person is unconscious, call 911.
Low Blood Sugar During Sleep
Nocturnal hypoglycemia is particularly tricky because you can’t notice symptoms while you’re asleep. Warning signs include restless or irritable sleep, waking up drenched in sweat, nightmares, trembling, and sudden changes in breathing pattern. A partner may notice these before you do.
If nighttime lows are a recurring problem, the typical solutions involve adjusting medication timing or doses, setting an alarm to check blood sugar in the early morning hours, or wearing a continuous glucose monitor that sounds an alarm when levels start dropping. A bedtime snack with protein and complex carbohydrates can also help keep levels stable overnight.
When Your Body Stops Warning You
One of the more dangerous complications of repeated low blood sugar is called hypoglycemia unawareness. Normally, symptoms like shaking and sweating alert you early enough to act. But if you experience frequent episodes, your body recalibrates: the glucose level that triggers those warning signs keeps getting lower and lower. Eventually, you may not feel anything until your blood sugar is dangerously low, and by that point you could already be confused or losing consciousness.
This is most common in people who have had diabetes for 20 or 30 years, those who aim for very tight glucose control, and people with cognitive impairment, depression, or anxiety that makes diabetes management harder. The consequences go beyond a single episode. People who experience severe hypoglycemia have a higher risk of heart attack or stroke in the following year, and recurrent episodes may contribute to long-term problems with brain and heart function. The risk of accidents, both driving and at work, also rises significantly when you can’t feel your blood sugar dropping.
The good news is that hypoglycemia unawareness can sometimes be reversed. Carefully avoiding any low blood sugar episodes for several weeks can help reset the threshold at which your body triggers warning symptoms, restoring your ability to catch a drop before it becomes dangerous.