A blood sugar level below 70 mg/dL (3.9 mmol/L) is considered low. At this threshold, your body starts mounting a hormonal defense to push glucose back up, and you may begin to feel early warning signs like shakiness or hunger. How far below 70 your blood sugar drops determines whether the situation is a mild inconvenience or a medical emergency.
The Three Levels of Low Blood Sugar
The American Diabetes Association classifies hypoglycemia into three levels based on severity. Level 1 is a blood sugar between 54 and 69 mg/dL. This is where most people first notice something feels off. Your body responds by dialing back insulin production and releasing glucagon, a hormone that signals the liver to release stored glucose. Level 1 episodes are common in people who take insulin or certain diabetes medications, and they can usually be corrected with a small amount of food.
Level 2 begins below 54 mg/dL (3.0 mmol/L). At this point, your brain isn’t getting enough glucose to function normally. Thinking becomes foggy, vision may blur, and speech can start to slur. This requires immediate action to bring blood sugar back up.
Level 3 is defined not by a specific number but by what’s happening to you: your mental or physical state is so impaired that you need someone else to help you. This can mean confusion so severe you can’t feed yourself, a seizure, or loss of consciousness. Level 3 hypoglycemia is a medical emergency regardless of what a glucose reading shows.
What Low Blood Sugar Feels Like
The earliest symptoms come from your body’s stress response. When blood sugar drops, your adrenal glands release adrenaline and related hormones to mobilize stored energy. That surge produces symptoms you’d recognize from any adrenaline rush: shaking, sweating, a pounding or racing heart, and sudden intense hunger. You might also feel anxious, irritable, or lightheaded. Some people notice tingling in their lips, tongue, or cheeks, or see the color drain from their skin.
As blood sugar falls further and your brain begins running short on fuel, a second set of symptoms appears. These are harder to self-detect because they affect your ability to think clearly. Confusion, difficulty concentrating, blurred or double vision, slurred speech, and poor coordination all signal that your brain is struggling. At the most severe end, seizures and loss of consciousness can occur. This is why low blood sugar can be dangerous: the very organ you need to recognize the problem and fix it is the one being affected.
Low Blood Sugar During Sleep
Hypoglycemia can happen overnight, and you may not wake up to treat it. Nighttime episodes tend to show up indirectly. You might sweat through your pajamas, have vivid nightmares, or wake up feeling exhausted, confused, or with a headache. A bed partner might notice restless sleep, trembling, sudden changes in your breathing pattern, or crying out.
Several factors raise the risk of overnight lows: skipping dinner, exercising close to bedtime, drinking alcohol in the evening, or being on a type of insulin that peaks six to eight hours after injection (meaning a dinnertime dose hits hardest in the middle of the night). If you’re waking up with unexplained symptoms, checking your blood sugar at 2 or 3 a.m. for a few nights can reveal a pattern.
How Your Body Fights Back
Your body has a layered defense system against falling blood sugar, and each layer kicks in at a progressively lower glucose level. The first response is simply reducing insulin output. Less insulin means your tissues absorb less glucose, and the liver is freed up to start releasing its stored supply.
If blood sugar keeps dropping, the pancreas releases glucagon. This hormone triggers the liver to break down glycogen (its short-term glucose reserve) and ramp up production of new glucose from other building blocks like amino acids. Glucagon is the body’s primary rescue hormone for low blood sugar, and it works within minutes.
When glucose falls further, into the mid-50s to upper-60s range, adrenaline enters the picture. It does many of the same things glucagon does, pushing the liver to produce more glucose, but it also suppresses insulin and causes fat tissue to release fatty acids as an alternative fuel source. The sweating, shaking, and rapid heartbeat you feel during a low are side effects of this adrenaline surge. In more severe episodes, cortisol and growth hormone join the response. These work more slowly, over hours rather than minutes, to sustain blood sugar by keeping the liver producing glucose and making your tissues more resistant to insulin’s effects.
Can Blood Sugar Drop if You Don’t Have Diabetes?
Yes. Low blood sugar in people without diabetes is less common but does happen. The diagnosis requires three things occurring together, a framework known as Whipple’s triad: you have symptoms consistent with hypoglycemia, a lab test confirms your blood sugar is genuinely low at the time of those symptoms, and the symptoms go away once your blood sugar comes back up. All three must be present because many of the symptoms of low blood sugar (shakiness, anxiety, sweating) overlap with other conditions.
In people without diabetes, causes can include prolonged fasting, heavy alcohol consumption, certain medications, hormonal deficiencies, or rarely a tumor in the pancreas that overproduces insulin. Reactive hypoglycemia, where blood sugar dips a few hours after eating (especially after a high-carbohydrate meal), is another pattern some people experience. If you’re having repeated episodes of symptoms that feel like low blood sugar, getting a plasma glucose measurement from a lab during an episode is the most reliable way to confirm what’s happening.
How to Treat a Low in the Moment
The standard approach is called the 15-15 rule: eat 15 grams of fast-acting carbohydrate, wait 15 minutes, then check your blood sugar again. If it’s still below 70 mg/dL, repeat. Practical options that deliver roughly 15 grams of carbohydrate include three glucose tablets, half a cup (4 ounces) of fruit juice or regular soda, six or seven hard candies, or one tablespoon of sugar.
Speed matters here. You want simple sugars that hit your bloodstream quickly, not complex carbohydrates or foods high in fat and protein. A candy bar or peanut butter crackers will eventually raise your blood sugar, but they digest too slowly when minutes count. Once your blood sugar is back in a safe range, follow up with a more substantial snack or meal to keep it stable.
For severe episodes where someone has lost consciousness or is having a seizure, do not put food or liquid in their mouth. They could choke. Glucagon, an injectable or nasal emergency medicine, is designed for exactly this situation. It works by triggering the liver to dump its glucose stores into the bloodstream. If someone in your household is at risk for severe lows, having a glucagon kit accessible and making sure family members know how to use it can be lifesaving.
A Note on Glucose Monitor Accuracy
If you use a continuous glucose monitor, keep in mind that readings at lower blood sugar levels can be less precise than at normal levels. For glucose values under 100 mg/dL, a continuous monitor is considered accurate if it falls within 15 mg/dL of a fingerstick reading. That means a monitor showing 65 mg/dL could reflect an actual blood sugar anywhere from 50 to 80. If your monitor alerts you to a low and you feel fine, or if you feel symptoms of a low but your monitor looks normal, a fingerstick test gives a more reliable number to act on.