Blood Glucose 19 tested - mmol/L or mg/dL?
Most meters outside the US show mmol/L. A reading of 19 is far more likely to be 19 mmol/L than 19 mg/dL.
If it is 19 mmol/L
= 342 mg/dL. Fasting without diabetes: Diabetes range · With diabetes before a meal: Very high
Full explanation for 342 mg/dL →If it really is 19 mg/dL
That is 1.1 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 19 mg/dL →Get medical advice now
- Check ketones if you use insulin. Moderate or high ketones, vomiting, abdominal pain, deep fast breathing or fruity-smelling breath can mean diabetic ketoacidosis — call 911 (US) or your local emergency number or go to the emergency room.
- Very high readings (especially above 33.3 mmol/L = 600 mg/dL, often shown as "HI") with extreme thirst, confusion or drowsiness can mean hyperosmolar hyperglycemic state — an emergency.
- With diabetes and none of these signs: contact your care team today and re-check every 2–3 hours.
- Without known diabetes: see a doctor today.
If you don't have diabetes — reading 19 mmol/L (342 mg/dL)
19 mmol/L (342 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 today.
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 range2 hours after eating (or glucose tolerance test)
Diabetes rangeIf you have diabetes — reading 19 mmol/L (342 mg/dL)
19 mmol/L (342 mg/dL) is very high. Check ketones if you use insulin and contact your care team today. With moderate or high ketones, vomiting, abdominal pain, deep fast breathing, extreme thirst, confusion or drowsiness, call 911 (US) or your local emergency number (see the box above).
Before a meal / fasting
Very high1–2 hours after a meal
Very highTargets 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.
342 mg/dL as an average: HbA1c 13.5%
If 342 mg/dL were your average glucose over two to three months, it would match an HbA1c of about 13.5% (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 342 mg/dL that means roughly 291–393 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 · MedlinePlus: Diabetic ketoacidosis · 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.