Low Blood Sugar (Hypoglycemia): Symptoms, Severe Lows, Night-Time Lows and Unawareness

Blood sugar changes often during the day. When it drops below 70 mg/dL, that is low blood sugar, and you need to act to bring it back up. It is especially common in people with type 1 diabetes, and it can be dangerous if left untreated — which is why it matters to know how to spot it.

People with diabetes can have low blood sugar as often as once or twice a week, even when they manage their blood sugar closely. Knowing how to identify it and treat it is important for your health.

Symptoms

Your reaction to low blood sugar may not be the same as someone else's, so learn your own symptoms. Common ones include:

• a fast heartbeat
• shaking
• sweating
• nervousness or anxiety
• irritability or confusion
• dizziness
• hunger

Severe low blood sugar

Below 54 mg/dL is severe. As a low gets worse, symptoms can become more serious:

• feeling weak
• trouble walking or seeing clearly
• acting strangely or feeling confused
• seizures

Blood sugar this low may make you faint (pass out), and you will often need someone to help you treat it.

Lows at night

Low blood sugar can happen at any time, including while you sleep. Reasons include:

• an active day
• physical activity close to bedtime
• taking too much insulin
• drinking alcohol at night

To help avoid it:

• Eat regular meals and do not skip them.
• Eat when you drink alcohol.
• Have a snack before bed if you think you are at risk overnight.

You may wake up when your blood sugar is low, but do not rely on it. A continuous glucose monitor (CGM) can alert you if your blood sugar drops while you sleep.

Hypoglycemia unawareness

You may have no symptoms at all when your blood sugar is low. That is hypoglycemia unawareness, and it is dangerous: without symptoms it is harder to treat a low early, so the risk of severe lows goes up. It is more likely if you:

• have had diabetes for more than 5–10 years
• often have low blood sugar
• take certain medicines, such as beta blockers for high blood pressure

If any of these apply and you have hypoglycemia unawareness, check your blood sugar more often — especially before driving or being physically active.

Causes

Many things can bring on low blood sugar:

Sources

Based on "Low Blood Sugar (Hypoglycemia)," Centers for Disease Control and Prevention; a work of the United States government in the public domain. The page's photograph was a stock image and is not reproduced.