A blood sugar reading below 70 mg/dL is generally considered low. For people with diabetes, that’s the first threshold where action is recommended. For people without diabetes, the clinical cutoff is slightly lower, at 55 mg/dL, because the body is typically better at correcting small dips on its own. Either way, the lower blood sugar drops, the more urgent the situation becomes.
The Three Levels of Low Blood Sugar
The American Diabetes Association breaks hypoglycemia into three levels based on severity. These thresholds apply to people with diabetes and are used widely in clinical settings.
- Level 1 (mild): Blood sugar between 54 and 69 mg/dL. You’ll likely notice symptoms, and eating a quick source of sugar will usually resolve it.
- Level 2 (moderate): Blood sugar below 54 mg/dL. At this point, your brain isn’t getting enough fuel to function normally. You need to act immediately.
- Level 3 (severe): Any episode where you’re too confused, disoriented, or physically impaired to treat yourself and need someone else’s help. This classification applies regardless of what the number on your meter says.
The jump from level 1 to level 2 matters because 54 mg/dL is roughly where neurological symptoms start. Mild shakiness is one thing. Confusion, slurred speech, and loss of coordination are a different category of risk entirely.
What Low Blood Sugar Feels Like
Symptoms arrive in a loose sequence. Early on, your body releases stress hormones to push blood sugar back up, and those hormones produce the first wave of warning signs: sweating, shakiness, a racing heart, anxiety, and sudden intense hunger. These are your body’s alarm bells, and they’re hard to miss once you learn to recognize them.
If blood sugar keeps falling, the symptoms shift. Your brain, which depends almost entirely on glucose for energy, starts to struggle. This produces a second set of symptoms: weakness, dizziness, difficulty concentrating, blurred vision, and confusion. Some people behave erratically enough to be mistaken for being drunk. In extreme cases, seizures or loss of consciousness can follow.
Not everyone feels the early warning signs. People who experience frequent lows can develop what’s called hypoglycemia unawareness, where the body stops sending those initial stress-hormone signals. If that happens to you, the first symptom you notice may already be confusion or poor coordination, which makes it harder to self-treat.
Low Blood Sugar During Sleep
Nighttime lows are particularly tricky because you’re asleep through the warning signs. Clues that it happened overnight include waking up drenched in sweat, having vivid nightmares, feeling unusually tired in the morning, or waking with a headache. Paradoxically, your morning blood sugar reading may actually be higher than normal, because the body rebounds from an overnight low by flooding the bloodstream with stored glucose.
If you use insulin and want to reduce the risk of nighttime lows, the Joslin Diabetes Center recommends checking your blood sugar at bedtime and aiming for a reading between 90 and 150 mg/dL before sleep. Skipping dinner or your usual evening snack increases the likelihood of a drop overnight. A small bedtime snack that includes some protein or fat, which digest slowly, can help keep levels stable through the night.
Why Blood Sugar Drops
For people with diabetes, the most common cause is too much insulin or other blood sugar-lowering medication relative to how much you’ve eaten or how active you’ve been. A larger-than-usual dose, a skipped meal, or unexpected exercise can all tip the balance.
For people without diabetes, the picture is more varied. Reactive hypoglycemia causes blood sugar to drop within four hours of eating, often because the body overproduces insulin in response to a meal. The exact trigger isn’t always clear, but it tends to be linked to what and when a person eats, particularly meals heavy in refined carbohydrates.
Other causes include alcohol consumption, certain bariatric surgeries, inherited metabolic conditions, and rare tumors that affect insulin production. Alcohol deserves special mention: it blocks the liver’s ability to produce new glucose. Normally, when blood sugar dips, your liver converts stored energy into glucose and releases it. Alcohol disrupts that process, which means your blood sugar can keep falling without the usual safety net. This risk is highest when drinking on an empty stomach or after heavy drinking.
How to Treat a Low
The standard approach is the 15-15 rule: eat 15 grams of fast-acting carbohydrates, then wait 15 minutes. If you don’t feel better or your reading is still low, repeat. Good options for those 15 grams include four glucose tablets, half a cup of juice, or a tablespoon of honey. The key is choosing something that’s mostly simple sugar with no fat or protein to slow absorption. A candy bar, for example, won’t raise blood sugar as quickly as juice because the fat content delays digestion.
Once your blood sugar recovers, follow up with a small meal or snack that includes protein or complex carbohydrates. The fast-acting sugar will wear off, and without something more substantial, you risk dropping again.
When Someone Can’t Self-Treat
If a person is too confused, unresponsive, or unable to swallow safely, giving them food or liquid is a choking hazard. This is where emergency glucagon comes in. Glucagon is a hormone that signals the liver to release its stored glucose into the bloodstream. It’s available as a nasal spray or an injection, and both can be administered by someone without medical training. If you live with someone who uses insulin, having a glucagon kit accessible and knowing how to use it before an emergency matters.
A severe episode where someone loses consciousness or has a seizure calls for emergency medical services, even if glucagon is given. Recovery from a severe low can take hours, and the person may feel wiped out for the rest of the day.
What Ranges Are Normal
For context, fasting blood sugar in a healthy person typically sits between 70 and 100 mg/dL. After a meal, it may rise to 140 mg/dL or so before settling back down within a couple of hours. Brief dips into the low-to-mid 60s can happen in healthy people without causing problems, which is why the diagnostic threshold for non-diabetic hypoglycemia is set at 55 mg/dL rather than 70. The body has multiple backup systems for keeping blood sugar in range, and in most people, those systems work well enough that a slight dip self-corrects before symptoms appear.
If you’re consistently seeing readings below 70 mg/dL or experiencing symptoms of low blood sugar and you don’t have diabetes, that pattern is worth investigating. Persistent or recurring lows can point to an underlying cause that benefits from diagnosis.