How to Lower High Blood Glucose Quickly

There is no instant trick for high blood sugar, but a few steps bring it down safely within hours. The fastest tool — insulin — is only for people who already use it as prescribed. Just as important: knowing when high glucose is an emergency.

1. Confirm the reading

Wash your hands with water and re-test. Traces of fruit, juice or sugar on your fingertip can push a reading up by 100 mg/dL or more.

2. Take correction insulin — if prescribed

If you use insulin, your care team has probably given you a correction factor (how much one unit lowers your glucose). Rapid-acting insulin starts working in about 15 minutes and peaks after 1–2 hours. Avoid "stacking" doses: wait at least 2–3 hours before correcting again, or you risk a low later.

3. Check ketones above 240 mg/dL

With type 1 diabetes, LADA or insulin-treated type 2 diabetes, test for ketones with urine strips or a blood ketone meter. Small ketones: more fluids and insulin as advised. Moderate or large ketones: call your care team or seek emergency care.

4. Drink water

High glucose pulls water out through the kidneys. Drinking water or other sugar-free fluids replaces it and helps the kidneys clear excess glucose. Avoid juice, regular soda and sports drinks.

5. Move — if it is safe

A 15–30 minute walk makes muscles take up glucose even with less insulin. Don't exercise if ketones are present, if you feel unwell, or if glucose is above about 300 mg/dL without a plan from your care team — exercise can then push glucose higher.

6. Look at the next meal

Choose vegetables, protein and healthy fats, and keep starchy and sugary foods small until you are back in range. Protein does not lower glucose directly, but it does not raise it much either.

7. Find the cause

• Missed or late dose? Expired or overheated insulin? Pump or infusion set problem?
• Larger meal than usual, or a hidden source of sugar?
• Illness, infection, stress, steroids?

Follow your sick-day plan when you are ill: keep taking insulin, test more often, drink plenty.

Without diabetes?

If you don't have diabetes and see a high reading, re-check fasting the next morning. Repeated values of 126 mg/dL or more fasting — or 200 mg/dL or more at any time with symptoms — need a doctor's assessment. More: High Blood Sugar (Hyperglycemia): Levels & Signs.