Blood Glucose 13 tested - mmol/L or mg/dL?

Most meters outside the US show mmol/L. A reading of 13 is far more likely to be 13 mmol/L than 13 mg/dL.

If it is 13 mmol/L

= 234 mg/dL. Fasting without diabetes: Diabetes range · With diabetes before a meal: High

If it really is 13 mg/dL

That is 0.7 mmol/L — severely low, below the level 2 hypoglycemia threshold of 54 mg/dL (3.0 mmol/L). 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-acting carbohydrate if they can swallow safely; if not, glucagon if available, recovery position and call 911 (US) or your local emergency number.

Full explanation for 13 mg/dL →

Bring it back into range

Drink water or other sugar-free fluids.
If you use insulin, take a correction dose only as your care team prescribed.
A 15–30 minute walk lowers glucose for many people — if you feel well.
Without diabetes: repeat the test after washing your hands (sugar on the fingers gives falsely high results); if it is confirmed, see a doctor soon.

If you don't have diabetes — reading 13 mmol/L (234 mg/dL)

13 mmol/L (234 mg/dL) is in the diabetes range whether fasting or after a meal. A random reading of 11.1 mmol/L = 200 mg/dL or more together with typical symptoms (thirst, frequent urination, weight loss) is enough for a diagnosis — see a doctor soon.

Fasting prediabetes cut-off: the ADA uses 5.6 mmol/L (100 mg/dL); the WHO uses 6.1 mmol/L (110 mg/dL). This site follows the ADA.

Fasting (8+ hours without food)

Diabetes range

2 hours after eating (or glucose tolerance test)

Diabetes range

If you have diabetes — reading 13 mmol/L (234 mg/dL)

13 mmol/L (234 mg/dL) is high — above both targets. Common causes: a carb-heavy meal, a missed or too-small dose, illness, stress or less activity than usual.

Before a meal / fasting

High

1–2 hours after a meal

Above target

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.

234 mg/dL as an average: HbA1c 9.8%

If 234 mg/dL were your average glucose over two to three months, it would match an HbA1c of about 9.8% (above the common treatment goal of below 7%). 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 234 mg/dL that means roughly 199–269 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

Sources: ADA Standards of Care · ADA: Hyperglycemia · ADAG study (HbA1c and average glucose) · WHO: Definition and diagnosis of diabetes · 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.