BloodGlucoseValueUnderstand every reading

Blood glucose 5 — mmol/L or mg/dL?

90mg/dL5.0 mmol/L

Most meters outside the US show mmol/L. A reading of 5 is far more likely to be 5 mmol/L than 5 mg/dL.

If it is 5 mmol/L

= 90 mg/dL. Fasting without diabetes: Normal · With diabetes before a meal: In target

Full explanation for 90 mg/dL →

If it really is 5 mg/dL

That is 0.3 mmol/L — severely low. Most meters show "LO" below 20 mg/dL. If the person is shaky, sweaty, confused or drowsy, treat it as a severe low: 15–20 g of fast sugar if they can swallow safely; if not, glucagon if available, recovery position and call 911 (US) or your local emergency number.

No immediate action needed

  • Note the time and whether you had eaten — the same number means different things fasting and after a meal.
  • Looking at the pattern over days (or a CGM report) tells you more than one reading.

If you don't have diabetes — reading 5 mmol/L (90 mg/dL)

90 mg/dL is a normal blood sugar both fasting and after a meal. Nothing to do.

Fasting (8+ hours without food)

NormalScale with 90 mg/dL marked5510012690 mg/dL

2 hours after eating (or glucose tolerance test)

NormalScale with 90 mg/dL marked5514020090 mg/dL

If you have diabetes — reading 5 mmol/L (90 mg/dL)

90 mg/dL is in target both before and after meals for most adults with diabetes (pre-meal 80–130, after meals below 180 mg/dL).

Before a meal / fasting

In targetScale with 90 mg/dL marked548013118124130090 mg/dL

1–2 hours after a meal

In targetScale with 90 mg/dL marked5418024130090 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.

90 mg/dL as an average: HbA1c 4.8%

If 90 mg/dL were your average glucose over two to three months, it would match an HbA1c of about 4.8% (normal range). A single reading says little about your HbA1c — it is the long-term average that counts. Learn more in how to measure blood sugar.

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 90 mg/dL that means roughly 77–103 mg/dL.
  • CGM sensors measure tissue fluid and lag 5–15 minutes behind blood when glucose changes quickly — confirm lows with a finger-stick.

Check another reading

Nearby values

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.