Hypoglycemia Symptoms: What Low Blood Sugar Feels Like and What to Do

What low blood sugar feels like

Symptoms come in two waves. First, the body releases adrenaline to raise sugar. Then, if sugar keeps falling, the brain runs short of fuel.

At night, lows can cause nightmares, crying out, sweating through sheets, and a headache or confusion on waking.

In young children, lows show as sudden crankiness, crying, pallor or unusual sleepiness.

Some people, especially after many years of diabetes or frequent lows, lose the early warning signs. This is hypoglycemia unawareness, and it raises the risk of severe episodes.

What to do: the 15-15 rule

If you have a glucose meter or CGM, check first. If you cannot check, treat anyway.

1. Take 15 grams of fast-acting sugar, for example: - 4 glucose tablets (check the label) - half a cup (4 oz, 120 ml) of regular juice or regular soda (not diet) - 1 tablespoon of sugar or honey - hard candies or jelly beans (check the label for amount)
2. Wait 15 minutes and recheck.
3. If still below 70 mg/dL (3.9 mmol/L), repeat.
4. Once above 70, eat a snack or meal with carbohydrate and protein if your next meal is more than an hour away.

Chocolate, nuts and other high-fat foods raise sugar too slowly. Children may need smaller amounts. Follow your care team's plan.

Helping someone who is very low

• If they are awake and can swallow, give sugar as above, sitting upright.
• If they are drowsy, confused, unconscious or seizing: do not put food or drink in their mouth (choking risk). Give glucagon (nasal powder, auto-injector or injection kit) if they have it, and follow the device instructions. Roll them onto their side. Call 911.
• Glucagon may cause vomiting, so keep them on their side. They should eat once they can swallow safely.

Insulin overdose and insulin pumps

A large insulin dose, especially long-acting insulin, or an overdose of sulfonylurea tablets can cause repeated, prolonged lows for 24 hours or more. Even if the person wakes after sugar or glucagon, they need hospital monitoring, IV glucose and observation. If someone on an insulin pump has a severe low or the pump may be malfunctioning, stop the insulin by suspending the pump or disconnecting the tubing, then treat the low. Bring the pump to the hospital.

In hospital, treatment includes IV dextrose, a continuous glucose infusion, frequent fingerstick checks, potassium monitoring, and, for sulfonylurea overdose, a medicine called octreotide. A deliberate overdose also needs a mental health assessment.

Common causes of a low

• too much insulin, or insulin taken without eating
• a delayed or missed meal, or fewer carbs than planned
• more exercise than usual, including for up to 24 hours afterward
• alcohol, especially without food (it blocks the liver from releasing sugar)
• sulfonylureas such as glipizide or glyburide, especially with kidney problems
• weight loss or illness changing insulin needs

People without diabetes rarely have true hypoglycemia. Possible causes include reactive hypoglycemia after meals, stomach surgery, heavy drinking, some medicines, severe illness and, rarely, an insulinoma. See hypoglycemia for the full list and how it is diagnosed.

Preventing lows

• Carry fast-acting sugar and wear medical ID.
• Check sugar before driving, exercise and bed. Treat a low before driving; UK guidance uses 5 mmol/L (90 mg/dL) as the minimum level to drive.
• Use a continuous glucose monitor with low alerts if available.
• Eat carbohydrate with alcohol, and check sugar overnight after drinking.
• Teach family, friends and coworkers how to use glucagon.
• Review your doses with your care team after any severe low.

Frequently asked questions

What are the first signs of low blood sugar?

The first signs are usually shakiness, sweating, a fast heartbeat, hunger, anxiety and tingling around the lips. If sugar keeps falling, confusion, blurred vision, slurred speech and drowsiness follow. Treat early symptoms straight away with fast-acting sugar.

What is the 15-15 rule for hypoglycemia?

Take 15 grams of fast-acting carbohydrate, such as 4 glucose tablets or half a cup of juice, wait 15 minutes and recheck your sugar. Repeat if it is still below 70 mg/dL (3.9 mmol/L). Once it is back up, eat a snack if your next meal is not soon.

When should you call 911 for low blood sugar?

Call 911 if the person is unconscious, having a seizure, cannot swallow safely, does not improve after treatment, or has taken too much insulin or diabetes medicine. Also call if glucagon was needed and they do not wake within 15 minutes.

Can you have low blood sugar without diabetes?

Yes, but it is uncommon. Causes include reactive hypoglycemia after meals, previous stomach surgery, heavy alcohol use, some medicines, severe illness and, rarely, insulin-producing tumors. A doctor confirms it by measuring blood sugar during symptoms.

Why is low blood sugar dangerous while driving?

Even moderate lows slow reaction time and judgment before you notice symptoms. Check before driving, keep sugar in the car, and if you feel low, pull over, treat it, and wait until your level has been back to normal for at least 45 minutes.