A blood sugar level below 70 mg/dL is generally considered too low. This threshold applies to people with diabetes and serves as the point where your body starts mounting a hormonal response to bring glucose back up. For people without diabetes, the diagnostic cutoff is slightly lower, at 55 mg/dL, because their bodies are typically better at correcting small dips before symptoms develop. Either way, the lower your blood sugar drops, the more serious the situation becomes.
The Three Levels of Low Blood Sugar
Not all lows are created equal. The American Diabetes Association breaks hypoglycemia into three levels based on how far blood sugar has fallen and how much help you need to recover.
Level 1 covers readings between 54 and 69 mg/dL. This is a mild low. You’ll likely feel early warning signs like shakiness, sweating, a racing heart, anxiety, or sudden hunger. These symptoms come from your body’s stress response kicking in to push glucose back into your bloodstream. Most people can treat a Level 1 low on their own with a quick source of sugar.
Level 2 begins below 54 mg/dL. At this point, your brain isn’t getting enough fuel. Symptoms shift from the physical stress response to cognitive problems: confusion, difficulty concentrating, irritability, blurred vision, and trouble speaking or walking. This level requires immediate action.
Level 3 is any episode severe enough that you can’t treat it yourself. It doesn’t matter what the number on the meter says. If someone needs another person’s help to recover, whether because of seizures, loss of consciousness, or extreme confusion, it qualifies as a severe event.
How Symptoms Change as Blood Sugar Drops
Your body responds to falling blood sugar in a predictable sequence. The first wave of symptoms is driven by adrenaline: sweating, trembling, palpitations, anxiety, and intense hunger. These warning signs typically show up in the 55 to 69 mg/dL range and act as an early alarm system, giving you a chance to eat something before things get worse.
If blood sugar keeps dropping, the second wave hits. These are brain-related symptoms caused by your neurons running short on their primary fuel. Confusion sets in. You may have trouble concentrating, become unusually irritable, or experience visual changes. In extreme cases, hallucinations, inability to move one side of the body, seizures, and loss of consciousness can occur. Without treatment, very severe hypoglycemia can be fatal, though this is rare.
One important complication: some people, especially those who experience frequent lows, lose the ability to feel the early warning signs. Their body stops mounting the adrenaline response, so they skip straight from feeling fine to being confused or disoriented. This is called hypoglycemia unawareness, and it makes low blood sugar significantly more dangerous because there’s no built-in alarm to prompt you to eat.
What Causes Blood Sugar to Drop Too Low
For people with diabetes, the most common cause is too much insulin or other glucose-lowering medication relative to what you’ve eaten or how active you’ve been. Skipping a meal, exercising more than usual, or misjudging a dose can all trigger a low. Alcohol also suppresses your liver’s ability to release stored glucose, which is why drinking on an empty stomach is a well-known trigger.
For people without diabetes, low blood sugar is less common but still possible. Causes include certain medications (some blood pressure drugs, lithium, and certain antibiotics can lower glucose), heavy alcohol use, liver or kidney disease, cortisol deficiency, and gastric or bariatric surgery, which changes how quickly food moves through your digestive system. Rarely, a tumor on the pancreas called an insulinoma produces excess insulin. There’s also reactive hypoglycemia, where blood sugar drops a few hours after eating, often due to an exaggerated insulin response to a meal.
Low Blood Sugar During Sleep
Nocturnal hypoglycemia is particularly tricky because you can’t feel the warning signs while you’re asleep. Clues that it happened include waking up with damp sheets or pajamas, having vivid nightmares, feeling unusually tired or groggy in the morning, or having a headache you can’t explain. A partner might notice restless sleep, shaking, rapid breathing, or sweaty skin.
The most common risk factors are skipping dinner, exercising close to bedtime, drinking alcohol in the evening, and taking certain types of insulin that peak overnight. A continuous glucose monitor with a low-glucose alarm is one of the most effective tools for catching these episodes, since it can wake you up when your levels start to fall.
How to Treat a Low in the Moment
The standard approach is called the 15-15 rule. Eat or drink 15 grams of fast-acting carbohydrates, then wait 15 minutes and recheck your blood sugar. If it’s still below 70 mg/dL, repeat. Keep going until you’re back in your target range.
Good options for those 15 grams include:
- 4 ounces (half a cup) of juice or regular soda
- 1 tablespoon of sugar, honey, or syrup
- 3 to 4 glucose tablets
- 1 tube of glucose gel
- A small handful of jellybeans or hard candies (check the label for serving size)
Speed matters here, so avoid foods high in fat or fiber. Chocolate, fruit, and baked goods all slow down sugar absorption. You want something that hits your bloodstream fast.
For severe episodes where someone is unconscious or unable to swallow, glucagon is the go-to treatment. It’s available as a nasal spray, a prefilled auto-injector, and a traditional injection kit. If you take insulin or are at risk for severe lows, keeping glucagon accessible and making sure the people around you know how to use it can be lifesaving.
When Low Blood Sugar Keeps Happening
A single mild low isn’t unusual for someone managing diabetes with insulin. But frequent lows, lows without warning symptoms, or lows that happen in someone without diabetes all warrant a closer look. For people without diabetes, the diagnostic process centers on something called Whipple’s triad: you have symptoms consistent with low blood sugar, a blood test confirms glucose is low at the time of symptoms, and the symptoms go away once blood sugar is corrected. All three need to be present to confirm the diagnosis and guide further testing.
Repeated lows in someone with diabetes usually mean something in the treatment plan needs adjusting, whether that’s medication timing, dosing, meal patterns, or activity levels. Repeated lows without clear cause in someone without diabetes may lead to additional testing for conditions like insulinoma, adrenal insufficiency, or autoimmune insulin syndromes.