Blood Glucose Tests for Diagnosing Diabetes

Blood Glucose Tests for Diagnosing Diabetes

How Are Diabetes and Prediabetes Diagnosed?

The following tests are used for the diagnosis of diabetes:

  • A fasting plasma glucose test procedures your blood sugar after you have gone at least 8 hours without consuming. This test is used to discover diabetes or prediabetes.
  • An oral glucose tolerance test measures your blood sugar after you have actually addressed least eight hours without eating and two hours after you drink a glucose-containing beverage. This test can be used to diagnose diabetes or prediabetes.
  • In a random plasma glucose test, your doctor checks your blood glucose without regard to when you ate your last meal. This test, together with an evaluation of symptoms, is used to diagnose diabetes, however not prediabetes.

Positive test outcomes need to be confirmed by duplicating the fasting plasma glucose test or the oral glucose tolerance test on a various day. When first diagnosed with diabetes, your doctor might suggest a zinc transporter 8 autoantibody (ZnT8Ab) test. This blood test — in addition to other details and test outcomes — can help identify if a person has type 1 diabetes and not another type. The objective of having the ZnT8Ab test is a timely and precise diagnosis which can result in timely treatment.

Fasting Plasma Glucose (FPG) Test

The FPG is most trustworthy when done in the early morning. Results and their meaning are displayed in table 1. If your fasting glucose level is 100 to 125 mg/dL, you have a kind of prediabetes called impaired fasting glucose (IFG), indicating that you are most likely to establish type 2 diabetes however do not have it yet. A level of 126 mg/dL or above, verified by duplicating the test on another day, suggests that you have diabetes.

Table 1. Fasting Plasma Glucose Test

Plasma Glucose Result (mg/dL) Diagnosis
99 and below Normal
100 to 125 Prediabetes

(impaired fasting glucose)

126 and above Diabetes*

*Confirmed by repeating the test on a different day.

Oral Glucose Tolerance Test (OGTT)

Research has shown that the OGTT is more delicate than the FPG test for detecting prediabetes, but it is less convenient to administer. The OGTT requires you to quick for a minimum of eight hours before the test. Your plasma glucose is determined immediately prior to and two hours after you drink a liquid containing 75 grams of glucose liquified in water. Outcomes and what they suggest are shown in table 2. If your blood sugar level is between 140 and 199 mg/dL 2 hours after drinking the liquid, you have a type of prediabetes called impaired glucose tolerance or IGT, suggesting that you are most likely to develop type 2 diabetes however do not have it yet. A two-hour glucose level of 200 mg/dL or above, validated by duplicating the test on another day, indicates that you have diabetes.

Table 2. Oral Glucose Tolerance Test

2-Hour Plasma Glucose Result (mg/dL) Diagnosis
139 and below Normal
140 to 199 Prediabetes

(impaired glucose tolerance)

200 and above Diabetes*

*Confirmed by repeating the test on a different day.

Gestational diabetes is likewise detected based upon plasma glucose values determined during the OGTT. Blood sugar levels are checked four times during the test. If your blood glucose levels are above normal a minimum of two times during the test, you have gestational diabetes. Table 3 shows the above-normal outcomes for the OGTT for gestational diabetes.

Table 3. Gestational Diabetes: Above-Normal Results for the Oral Glucose Tolerance Test

When Plasma Glucose Result (mg/dL)
Fasting 95 or higher
At 1 hour 180 or higher
At 2 hours 155 or higher
At 3 hours 140 or higher

Note: Some laboratories use other numbers for this test.

Gestational Diabetes – Treatment

Random Plasma Glucose Test

A random blood sugar level of 200 mg/dL or more, plus existence of the following symptoms, can suggest that you have diabetes:

  • Increased urination
  • Increased thirst
  • Unusual weight-loss

Other symptoms include fatigue, blurred vision, increased cravings, and sores that do not heal. Your doctor will inspect your blood sugar level on another day utilizing the FPG or the OGTT to confirm the diagnosis of diabetes.

Newer guidelines use hemoglobin A1c as a screening tool for prediabetes or diabetes (the test is normally used to measure blood glucose control in diabetes patients over several months). An HbA1c of 5.7% to 6.4% is consistent with prediabetes and marks a time when it can be reversed by lifestyle changes. An HbA1c of 6.5% or greater is consistent with diabetes.

Also read: How to Get Diabetes Testing Supplies

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