A blood glucose reading below 70 mg/dL (3.9 mmol/L) is considered low, and it needs your attention. Whether you checked with a home meter, got a lab result, or are feeling shaky and suspect a drop, low blood sugar (hypoglycemia) is one of the few situations where your body gives you clear signals that something needs to be corrected quickly. Most mild episodes resolve within 15 to 20 minutes with the right response.
What Counts as Low
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 feel symptoms, but you can treat it yourself. Level 2 is anything below 54 mg/dL, which is clinically significant and requires immediate action. Level 3 isn’t defined by a specific number. It’s any episode severe enough that you need someone else’s help to recover, usually because confusion, loss of consciousness, or seizures have set in.
If your reading is in the 60s, you’re in mild territory. If it’s in the 40s or lower, that’s a more urgent situation. Even a reading just under 70 is worth correcting, because blood sugar can keep dropping if you don’t intervene.
What It Feels Like
Your body responds to falling glucose in two waves. The first wave comes from your nervous system reacting to the drop. You may feel sweaty, shaky, or notice your heart pounding. Intense hunger, tingling in your lips or fingers, and a sudden wave of anxiety are also common early signs. These symptoms are your body’s alarm system, and they typically kick in while your glucose is still above 54 mg/dL.
If glucose keeps falling, a second set of symptoms appears. These come from your brain not getting enough fuel. You might feel weak, drowsy, or mentally foggy. Confusion, difficulty speaking, and trouble concentrating are hallmarks of this stage. In the most severe cases, seizures or loss of consciousness can occur. The transition between the two stages can happen quickly, which is why treating early symptoms promptly matters so much.
How to Treat a Low 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 glucose again. If it’s still below 70, repeat. Good sources of 15 grams of fast carbs include:
- 4 glucose tablets
- 4 ounces (half a cup) of juice or regular soda
- 1 tablespoon of honey or sugar
Avoid foods with fat or protein for this initial correction. A candy bar or peanut butter crackers will work eventually, but the fat slows digestion, and you need sugar in your bloodstream fast. Once your glucose is back above 70, eat a small meal or snack with protein and complex carbs to keep it stable.
If someone with low blood sugar is unconscious or unable to swallow safely, they should not be given food or drink. Glucagon, a hormone that triggers the liver to release stored sugar, is available as a nasal spray or a pre-filled auto-injector. The nasal spray requires no preparation: it’s sprayed into one nostril while the other is held closed. These are designed so a family member, coworker, or bystander can administer them without medical training. The person should be rolled onto their side to prevent choking.
Common Causes if You Have Diabetes
Diabetes medications are the most frequent cause of low blood sugar. Insulin itself is the biggest culprit, but oral medications called sulfonylureas (like glipizide or glyburide) are also well known for causing lows. These drugs stimulate your pancreas to release more insulin regardless of what your glucose is doing, which means a missed meal or extra exercise can tip you into hypoglycemia. Metformin, the most commonly prescribed diabetes drug, generally doesn’t cause lows on its own but can when combined with sulfonylureas.
Common triggers include eating less than usual, eating later than usual, exercising more intensely or longer than planned, and drinking alcohol. Alcohol is particularly tricky because it blocks your liver from releasing stored glucose, which is your body’s main backup system for maintaining blood sugar between meals. A drink or two with dinner may not cause problems, but drinking on an empty stomach or having several drinks can lead to a drop hours later, even while you sleep.
Low Blood Sugar Without Diabetes
If you don’t have diabetes and your glucose is low, the cause is less obvious but worth investigating. Non-diabetic hypoglycemia generally falls into two categories.
Reactive hypoglycemia happens after eating, typically two to four hours after a meal. Your body overproduces insulin in response to the food, and glucose drops below normal. This is more common after meals heavy in refined carbohydrates and in people who’ve had bariatric surgery.
Fasting hypoglycemia happens when you haven’t eaten for an extended period. Potential causes include liver or kidney disease, adrenal gland problems, a pituitary gland disorder, severe infection, or rarely a tumor called an insulinoma that produces excess insulin. Alcohol, anorexia nervosa, and certain medications can also trigger it. Some antibiotics (like levofloxacin and trimethoprim-sulfamethoxazole), heart rhythm medications, and even some pain relievers have been linked to blood sugar drops.
A single low reading doesn’t necessarily mean something is wrong. Skipping meals, intense exercise, or drinking alcohol can cause a one-time dip in anyone. But repeated episodes of low blood sugar without an obvious explanation deserve a medical workup.
Why Some People Stop Feeling Symptoms
If you experience frequent lows, your body can gradually stop sounding the alarm. This is called hypoglycemia unawareness, and it creates a dangerous cycle. Normally, your nervous system fires off warning signs like shakiness and sweating when glucose starts falling. But when lows happen repeatedly, your body recalibrates its threshold. The early warning symptoms don’t kick in until glucose is already dangerously low, or they don’t appear at all. You can go from feeling fine to confused or unconscious without the usual transition.
This is most common in people with long-standing type 1 diabetes, but it can happen to anyone who has frequent hypoglycemic episodes. The good news is that it’s often reversible. Carefully avoiding all lows for two to three weeks can help reset your body’s alarm system, restoring your ability to feel the early warning signs again.
Preventing Future Lows
If you take insulin or sulfonylureas, the most effective prevention is matching your medication to your actual food intake and activity level. Checking your glucose before bed is particularly important. Nighttime lows are hard to detect because you’re asleep, and they can cause morning headaches, damp sheets from sweating, and feeling unrested. If your bedtime glucose is trending toward the lower end, a small snack with slow-digesting carbohydrates and protein can help bridge the gap. People at higher risk for nighttime drops include those with long-standing diabetes, anyone who exercised heavily that day, and anyone who drank alcohol in the evening.
Continuous glucose monitors have changed the game for many people. These devices track glucose every few minutes and can sound an alarm when levels start dropping, catching a low before symptoms appear. They’re especially valuable for people with hypoglycemia unawareness.
For non-diabetic reactive hypoglycemia, eating smaller, more frequent meals and reducing refined carbohydrates can smooth out the insulin spikes that lead to post-meal crashes. Pairing carbs with protein, fat, or fiber slows digestion and keeps glucose more stable.