Blood Sugar 250 mg/dl — Is It Dangerous? What to Do Now
Where 250 mg/dl sits — adjust to your situation
250 mg/dl as a fasting reading
Very high (act now)
A fasting reading this high needs prompt medical attention, especially if you feel thirsty, tired or nauseous.
Fasting = no food for at least 8 hours, typically first thing in the morning. More on fasting readings.
250 mg/dl after eating
Very high (act now)
This is very high even right after a large meal, and needs prompt medical attention.
Guidelines measure 2 hours after the start of a meal. More on post-meal readings.
Measured right after exercise?
There is no official range for readings taken during or just after a workout, so the two classifications above do not apply to them. How exercise moves blood sugar.
How 250 mg/dl compares to a typical day
Typical day without diabetes; your reading is the horizontal line — above anything a typical day produces, even right after meals.
What to do with a reading of 250 mg/dl
Drink water, avoid carbohydrates, and contact your doctor today. If you have type 1 diabetes, check ketones now; with vomiting, deep breathing or confusion, call 911 (US) or your local emergency number.
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Questions about 250 mg/dl
Is 250 mg/dl blood sugar normal?
It depends on when you measured. Fasting, 250 mg/dl is very high (act now) (normal fasting range: 70–99 mg/dl). Two hours after a meal it is very high (act now) (normal post-meal range: 70–139 mg/dl).
What is 250 mg/dl in mmol/L?
250 mg/dl equals 13.9 mmol/L. Divide mg/dl by 18 to convert (used in the UK, Canada, Australia and most of Europe).
Does one reading of 250 mg/dl mean I have diabetes?
No single home reading is a diagnosis. Guidelines require a second abnormal lab result, either a different test from the same blood draw or a repeat on another day (fasting glucose, an oral tolerance test, or A1C). But a reading like this is exactly the reason those tests exist — take it to your doctor.
How accurate is a home reading of 250 mg/dl?
Home meters are allowed an error of ±15 mg/dl below 100 mg/dl and ±15 % from 100 up (ISO 15197), so a displayed 250 can correspond to a true value anywhere from 213 to 288 mg/dl. Fasting, that window crosses the 250 mg/dl line — a single home reading of 250 cannot settle which side you are truly on. That is a lab-test question, not a meter question.
What A1C would 250 mg/dl correspond to?
If 250 mg/dl were your average glucose over three months, it would work out to an A1C of about 10.3 % — at or above the 6.5 % diabetes threshold. A single reading is not an average — but the conversion shows what this level would mean as a habit. How the two measures relate: A1C and blood sugar.
Nearby values
Classification follows ADA criteria. This page explains a measurement — it does not diagnose.
BloodSugarEasy — blood sugar reading report
Reading: 250 mg/dl (13.9 mmol/L)
Fasting classification: Very high (act now) · After-meal classification: Very high (act now)
Reference: ADA criteria, reviewed 2026-08-21 · https://bloodsugareasy.com/blood-sugar-250/
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