BloodGlucoseValueUnderstand every reading

Blood Glucose 42 mg/dL tested - is it bad?

42mg/dL2.3 mmol/L
  • Without diabetes, fastingVery low
  • Without diabetes, 2 h after eatingVery low
  • With diabetes, before a mealLevel 2 hypoglycemia
  • With diabetes, after a mealLevel 2 hypoglycemia
  • In mmol/L2.3 mmol/L

Treat a low now

  • 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.
  • Re-check after 15 minutes. Still below 70 mg/dL? Repeat. Once above 70, eat a snack or meal.
  • If the person cannot swallow safely, is confused or unconscious: give glucagon if available, put them in the recovery position and call 911 (US) or your local emergency number. Never put food in the mouth of someone who is unconscious.
  • Without diabetes: a confirmed reading this low needs a doctor to find the cause.

If you don't have diabetes

42 mg/dL is well below normal. In people without diabetes, blood sugar rarely falls this low. If the reading is real and you have symptoms (shakiness, sweating, confusion), treat it now with 15–20 g of fast-acting carbohydrate (see the box above) and see a doctor to find the cause.

Fasting (8+ hours without food)

Very lowScale with 42 mg/dL marked557010012642 mg/dL

2 hours after eating (or glucose tolerance test)

Very lowScale with 42 mg/dL marked557014020042 mg/dL

If you have diabetes

42 mg/dL is level 2 hypoglycemia — clinically significant low blood sugar. Treat it immediately (see the box above). If it happens repeatedly, your treatment plan needs to change.

Before a meal / fasting

Level 2 hypoglycemiaScale with 42 mg/dL marked547080>130>180>24030042 mg/dL

1–2 hours after a meal

Level 2 hypoglycemiaScale with 42 mg/dL marked5470180>24030042 mg/dL

Targets for most non-pregnant adults (American Diabetes Association (ADA) Standards of Care). Your own targets may be different — for example in pregnancy, for children, older adults or people prone to lows. See pregnancy targets.

Make sure the number is right

  • Wash and dry your hands before a finger-stick: fruit juice or sugar on the skin can raise the result a lot.
  • Home meters may differ from a lab value by up to about 15%. At 42 mg/dL that means roughly 36–48 mg/dL.
  • CGM sensors measure tissue fluid and lag 5–15 minutes behind blood when glucose changes quickly — confirm lows with a finger-stick.

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Nearby values

Sources: ADA Standards of Care · ADA: Hypoglycemia · MedlinePlus: Blood glucose test

This page explains one reading in general terms. It is not a diagnosis or a treatment instruction. Follow the plan agreed with your doctor or diabetes team.