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Low Blood Sugar (Hypoglycemia): Levels & Treatment

Reviewed 2026-10-25 · How we write

Illustration of a dizzy woman sitting in an armchair holding a glass of orange juice

Low blood sugar — hypoglycemia — means glucose has dropped below 70 mg/dL (3.9 mmol/L). It happens most often in people who take insulin or certain diabetes tablets, and it needs quick treatment because the brain depends on glucose.

Levels of hypoglycemia

LevelGlucoseMeaning
Level 154–69 mg/dL (3.0–3.8 mmol/L)Low — treat with fast carbohydrate
Level 2below 54 mg/dL (3.0 mmol/L)Clinically significant — treat immediately
Level 3any valueSevere: confusion or unconsciousness, needs another person's help

Symptoms

Early: shakiness, sweating, fast heartbeat, hunger, anxiety, tingling lips, pale skin.
Later: difficulty concentrating, blurred vision, slurred speech, irritability or unusual behavior, weakness, clumsiness.
Severe: confusion, seizures, loss of consciousness.

At night, lows can cause nightmares, sweating and a headache on waking. Some people with long-standing diabetes lose the early warning signs — called hypoglycemia unawareness. A CGM with alarms is especially helpful then.

Treatment: the 15-15 rule

  1. Take 15–20 g of fast-acting carbohydrate: 4 glucose tablets, ½ cup (4 oz) of juice or regular soda, or 1 tablespoon of sugar or honey.
  2. Wait 15 minutes and check again.
  3. Still below 70 mg/dL? Repeat.
  4. Once above 70, eat a snack or meal with carbohydrate and protein to prevent another drop.

Avoid chocolate or fatty snacks for treating a low — fat slows absorption. Details: Raise Low Blood Glucose Fast: The 15-15 Rule.

Severe low: if someone cannot swallow safely, is confused or unconscious, do not give food or drink. Give glucagon (nasal spray or injection) if available, turn them on their side and call 911 (US) or your local emergency number. See diabetes first aid.

Common causes in diabetes

  • Too much insulin, or a dose not matched to the meal
  • Sulfonylureas (glipizide, glimepiride, glyburide)
  • Skipped or delayed meals
  • More exercise than usual — lows can occur up to 24 hours later
  • Alcohol, especially without food
  • Kidney problems (medication stays in the body longer)

Low blood sugar without diabetes

True hypoglycemia in people without diabetes is uncommon. Possible causes include reactive hypoglycemia 2–4 hours after a carbohydrate-rich meal (more common after stomach surgery), heavy drinking, some medications, severe illness, hormone deficiencies and, rarely, an insulin-producing tumor. Doctors look for "Whipple's triad": symptoms, a measured low level, and relief when glucose is raised. If you have repeated lows without diabetes, see a doctor.

Preventing lows

  • Always carry fast-acting glucose.
  • Check before driving — don't drive below 90 mg/dL without treating first — and before and after exercise.
  • Discuss dose adjustments with your care team if lows happen more than occasionally.
  • Make sure family, friends and colleagues know how to help, and keep glucagon at hand if you use insulin.

Check a reading: 65, 54 or 45 mg/dL.

Sources: ADA Standards of Care · ADA: Hypoglycemia · NIDDK: Low blood glucose · MedlinePlus: Low blood sugar self-care

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Educational content only; not medical advice. Follow the treatment plan you have agreed with your doctor or diabetes team. In an emergency, call 911 (US) or your local emergency number.