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# Hyperglycemia

hy·per·gly·ce·mi·a - hy-per-gly-SEE-mee-ah

## Definition

Hyperglycemia means abnormally high blood glucose (sugar) levels - generally defined as a fasting blood glucose above 125 mg/dL or a random blood glucose above 200 mg/dL. It is most commonly associated with diabetes mellitus, where the body either doesn't produce enough [insulin](/glossary/insulin) (type 1) or can't effectively use the insulin it produces (type 2), resulting in glucose accumulating in the bloodstream instead of being absorbed by cells.

Acute hyperglycemia can cause symptoms including increased thirst, frequent urination, blurred vision, fatigue, and headaches. If left untreated, severely elevated blood sugar can progress to dangerous conditions: diabetic ketoacidosis (DKA) in type 1 diabetes, or hyperosmolar hyperglycemic state (HHS) in [type 2 diabetes](/conditions/type-2-diabetes) - both of which are medical emergencies.

Chronic hyperglycemia - even at moderately elevated levels - causes progressive damage to blood vessels, nerves, eyes, kidneys, and the heart. This is why blood sugar management is the central focus of diabetes treatment. The microvascular complications of chronic hyperglycemia include retinopathy (eye damage), nephropathy (kidney damage), and neuropathy (nerve damage), while macrovascular complications include accelerated [atherosclerosis](/glossary/atherosclerosis) and increased risk of [heart attack](/glossary/myocardial-infarction) and stroke.

## Also Known As

High blood sugar Elevated glucose 

## Key Facts

-   • Fasting hyperglycemia is defined as blood glucose above 125 mg/dL; postprandial (after meals) above 180 mg/dL. 
-   • Common causes include diabetes, stress, illness, certain medications (steroids), and excessive carbohydrate intake. 
-   • The HbA1c test reflects average blood glucose over 2-3 months; a level above 6.5% indicates diabetes. 
-   • Even modest, sustained hyperglycemia increases the risk of cardiovascular disease, nerve damage, and kidney disease. 
-   • Exercise can acutely lower blood glucose by increasing cellular glucose uptake independent of insulin. 

## How It Relates To Your Health

Hyperglycemia management is the cornerstone of diabetes care. If you have diabetes, monitoring your [blood glucose](/glossary/blood-glucose) through fingerstick testing or continuous glucose monitors (CGMs) helps identify hyperglycemic episodes and guides medication, diet, and activity adjustments. Target blood glucose ranges are individualized based on age, diabetes type, and overall health.

Non-diabetic hyperglycemia can occur during acute illness, physiological stress, or as a medication side effect (particularly with corticosteroids). Persistently elevated fasting glucose in the 100-125 mg/dL range indicates prediabetes - a critical intervention window where lifestyle changes can prevent progression to diabetes.

## Related Terms

[Blood Glucose](/glossary/blood-glucose)[Insulin](/glossary/insulin)[Insulin Resistance](/glossary/insulin-resistance)[HbA1c](/glossary/hba1c)[Hypoglycemia](/glossary/hypoglycemia)[Metabolic Syndrome](/glossary/metabolic-syndrome)

## Sources

1.  [Hyperglycemia in Diabetes](https://www.mayoclinic.org/diseases-conditions/hyperglycemia/symptoms-causes/syc-20373631) - Mayo Clinic
2.  [Hyperglycemia](https://www.ncbi.nlm.nih.gov/books/NBK430900/) - StatPearls / PubMed
3.  [Managing Hyperglycemia](https://diabetes.org/about-diabetes/hyperglycemia) - American Diabetes Association

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[Definition](#definition)[Also Known As](#also-known-as)[Key Facts](#key-facts)[How It Relates To Your Health](#health-relevance)[Related Terms](#related-terms)[Sources](#sources)

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[Insulin Resistance](/glossary/insulin-resistance)[Thyroid-Stimulating Hormone](/glossary/thyroid-stimulating-hormone)[Metabolic Syndrome](/glossary/metabolic-syndrome)[HbA1c](/glossary/hba1c)[Adrenal Fatigue](/glossary/adrenal-fatigue)[Blood Glucose](/glossary/blood-glucose)

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