A blood glucose reading below 70 mg/dL is considered low, and it needs your attention. Most people feel the effects well before it becomes dangerous, but knowing what to do in the moment and understanding why it happened can prevent a minor dip from turning into a serious problem.
What Counts as Low Blood Sugar
The American Diabetes Association breaks low blood sugar into three levels. Level 1 is a reading between 54 and 69 mg/dL. You’ll likely notice symptoms, but you can treat it yourself. Level 2 is anything below 54 mg/dL, which is more serious and requires faster action. Level 3 isn’t defined by a specific number. It’s any episode where you’re too confused, disoriented, or unconscious to treat yourself and need someone else’s help.
These thresholds apply whether you have diabetes or not. A reading in the low 60s after skipping a meal might feel uncomfortable but resolve quickly. A reading in the 40s is a medical situation that demands immediate treatment.
How Low Blood Sugar Feels
Your body responds to falling glucose in two waves. The first is an adrenaline response: sweating, shakiness, a racing heart, anxiety, and sudden intense hunger. These symptoms are your early warning system, and they typically show up when glucose drops below 70 mg/dL.
If glucose keeps falling, your brain starts running short on fuel. That’s when the second wave hits: weakness, dizziness, trouble concentrating, blurred vision, and confusion. People in this state sometimes slur their words or behave erratically, which can be mistaken for intoxication. In extreme cases, it can lead to seizures or loss of consciousness.
In children, the picture is less predictable. Kids often show a mix of both responses at once, with behavioral changes and irritability rather than the textbook progression adults experience.
What to Do Right Now
The standard approach is called the 15-15 rule. Eat or drink 15 grams of fast-acting carbohydrates, then wait 15 minutes and check your blood sugar again. If it’s still below 70 mg/dL, repeat the process. Keep going until your levels are back in your target range. Good options for 15 grams of carbs include four glucose tablets, half a cup of juice or regular soda, or a tablespoon of honey.
Don’t overdo it. When you feel shaky and hungry, the impulse is to eat everything in sight. But overcorrecting with a large meal can send your blood sugar swinging too high in the other direction. Stick to 15 grams at a time, recheck, and once you’re stable, follow up with a small snack that includes some protein or fat to keep your levels steady.
If someone is unconscious or too confused to swallow safely, do not try to give them food or liquid. They could choke. This is when emergency glucagon is used. Glucagon comes as a pre-filled injection or auto-injector and is given as a shot in the stomach, thigh, or upper arm. If you or someone you live with is at risk for severe lows, having a glucagon kit on hand and knowing how to use it ahead of time is essential.
Common Causes if You Have Diabetes
For people taking insulin or certain diabetes medications, low blood sugar is one of the most common complications. The CDC lists four main triggers: taking too much insulin, not eating enough carbohydrates relative to your dose, mistiming your insulin, and physical activity. Any one of these can tip the balance.
Exercise deserves special attention because its effects aren’t always immediate. After a workout, especially one in the evening, your muscles continue pulling glucose from your blood for hours. Research shows the risk of a delayed low is highest 8 to 12 hours after exercise, which means an evening gym session could cause a dangerous drop in the middle of the night while you’re asleep.
Alcohol adds another layer of risk. Your liver normally releases stored glucose to keep levels stable between meals, but when it’s busy processing alcohol, that backup system slows down. Drinking on an empty stomach or combining alcohol with exercise creates a compounding effect that can catch people off guard hours later.
Low Blood Sugar Without Diabetes
If you don’t have diabetes and you’re experiencing symptoms of low blood sugar, the most common form is reactive hypoglycemia, where glucose drops a few hours after eating. The exact cause often isn’t clear, but it tends to be connected to what and when you eat. Meals heavy in refined carbohydrates can trigger a surge of insulin that overshoots and pulls glucose too low.
Other possible causes include alcohol, prior bariatric surgery (which changes how quickly food moves through your digestive system), inherited metabolic conditions, and rarely, certain types of tumors that produce excess insulin. If you’re getting repeated episodes without an obvious explanation, tracking when they happen relative to meals gives your doctor useful information to work with.
Why Some People Stop Feeling the Warning Signs
One of the more dangerous complications of repeated low blood sugar is something called hypoglycemia unawareness. The mechanism is straightforward but concerning: each time your body experiences a low, it recalibrates. If you had symptoms at 60 mg/dL yesterday, today you might not feel anything until you hit 55. Tomorrow, maybe 50.
The problem is that while your symptom threshold keeps dropping, the threshold for losing consciousness does not. The gap between “I feel fine” and “I’m unconscious” narrows until there’s almost no warning at all. People with hypoglycemia unawareness are at higher risk for car accidents, workplace injuries, and other situations where suddenly losing consciousness is dangerous. Research from the NIDDK also shows that a single episode of severe hypoglycemia raises the risk of heart attack or stroke in the following year.
Avoiding lows for several weeks can partially reset your body’s warning system, but this requires careful adjustment of medications and close glucose monitoring.
Low Blood Sugar During Sleep
Nocturnal hypoglycemia is particularly tricky because you can’t feel and respond to symptoms the way you would while awake. Warning signs that a bed partner might notice include restless sleep, sweating, trembling, sudden changes in breathing patterns, and nightmares. You might wake up with a headache, feeling exhausted, or with damp sheets.
The most common triggers are an active day, exercising close to bedtime, or taking too much insulin before bed. If nighttime lows are a recurring issue, a continuous glucose monitor with a low-glucose alarm can wake you before levels drop too far. These devices check blood sugar every five minutes and are particularly valuable for people who live alone or experience frequent overnight episodes.
Practical adjustments include having a small bedtime snack with slow-digesting carbohydrates, reviewing insulin timing with your care team, and monitoring glucose more closely on days when you’ve been unusually active.