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Blood Sugar Test

A blood sugar test, also referred to as a blood glucose test, is commonly used to measure blood glucose levels. There are four common types of blood sugar test—fasting, random, oral, and home. Testing blood glucose is important for patients with Type 1 diabetes, Type 2 diabetes, gestational diabetes, and prediabetes.

If a patient suffers from diabetes, the insulin/glucose balance does not work properly. After eating carbohydrates, blood glucose levels rise in the blood. The pancreas releases insulin to help cells utilize glucose for energy. If the body does not respond correctly to insulin, blood glucose levels can rise too high, causing symptoms of high blood sugar, including the three polyuria (increased urination), polydipsia (increased thirst), and polyphagia (increased hunger).

Fasting Blood Sugar Test & Results

A fasting blood sugar test is administered after a minimum fasting time of eight hours. Patients are asked to stop eating or drinking anything other than water the night before the test. Blood is drawn following the fast to measure the amount of glucose in the blood.

Normal blood glucose results during a fasting blood sugar test range from 59 to 109 mg/dL. If results fall between 110 and 125 mg/dL, patients are said to have borderline diabetes or pre-diabetes. Results falling at 126 mg/dL or above are a sign of diabetes. Generally, your doctor will want to see two fasting blood glucoses above 126 mg/dL to diagnose diabetes.

What is Insulin

Random Blood Sugar Test

A random blood sugar test follows no standard guidelines for eating, drinking or fasting. Blood is drawn at random times throughout the day to measure the patient's natural glucose level in their normal environment. If a patient is healthy with no signs of diabetes, results of each random blood glucose test should be approximately the same, as glucose levels rise and fall minimally in healthy patients. If the measurements vary widely, it could be a cause for additional testing.

Oral Blood Sugar Test

The oral blood sugar test, also known as the 2-hour test, measures the amount of glucose in blood two hours after the patient consumes a carbohydrate-rich snack or drink. This blood sugar test is most commonly used to test for gestational diabetes in pregnant patients. Patients must fast for eight hours before the test is completed.

Blood is drawn from patients before the glucose drink is administered to set a baseline glucose number. Then a glucose drink or snack containing 75 grams of glucose is consumed in the waiting room. Patients are called back two hours after the drink is administered to have blood drawn a second time. Normal glucose measurements should be at or below 140 mg/dL. Measurements that fall between 140 and 199 mg/dL are considered impaired glucose tolerance. If glucose levels are at or above 200 mg/dL, the patient may have gestational diabetes or diabetes type II. This will be determined by your doctor.

How to Prevent Diabetes

Home Blood Sugar Test

The home blood sugar test is likely the one most diabetes patients are familiar with. The test is administered by the patient and requires a small amount of blood for completion. Home blood testing machines involve a pinprick and testing of the blood by a home monitor. Diabetes patients use home blood sugar tests to monitor the rise and fall of glucose levels in association with food intake. Based on the results, patients may alter diet, use physician-prescribed insulin or take oral diabetes medications to help maintain healthy blood glucose levels.

Reviewed by Dr. Jennifer Monti, MD, MPH

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