Blood Tests That Indicate Diabetes

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What is Diabetes?

It is estimated that a staggering 7.8% of the American population has diabetes, approximately 23 million people. Of these, 17.9 million people have been diagnosed, but as many as 5.7 million people with the illness have not been given a diagnosis yet.

Diabetes is a disease of glucose management. When people consume food, the body breaks it down into simpler compounds, which it needs to thrive through the process of digestion. One of these metabolic products is glucose, the simplest form of sugar, which is the energy source used to power the body. For glucose to be useful, it needs to pass from the digestive system into the bloodstream where it can be carried throughout the body. Once glucose is in the bloodstream, it can supply the body’s cells with the energy they need to function. However, for this to happen, the glucose must be able to pass from the bloodstream and into the cell. A molecule called insulin is required to regulate the transfer of glucose from the bloodstream and into cells. Insulin is a hormone that is produced by the pancreas. In healthy people, the body will produce enough insulin to allow the transfer of the glucose produced by eating, from the bloodstream and into the cells.

In people with diabetes, the body does not produce enough insulin to regulate the amount of glucose within the bloodstream. The level of glucose in blood will rise, but the cells cannot access it. Eventually, some of the glucose will excreted into the urine via the kidneys.

There are three main types of diabetes:

Type 1 diabetes (an autoimmune disease)

Type 2 diabetes (accounts for 90 to 95% of all diabetic patients)

Gestational diabetes (occurs in late pregnancy and usually stops after the child is born)

Blood Tests

Blood tests that indicate diabetes reveal higher than normal blood glucose levels. The detection of glucose in blood can be achieved using an immobilized enzyme bioassay. In this type of devise, the glucose present in the blood sample is oxidized enzymatically, producing hydrogen peroxide, which is subsequently reduced at a platinum electrode. The current produced at the electrode is proportional to the concentration of glucose in the original blood sample.

Alternatively, there are many glucose meters on the market that use a blood sample obtained from a skin prick. A small amount of blood is placed on a test strip and the single use strip is then read by the meter. The test strips are specific for the meter being used, so if alternative suppliers of test strips are used, it is essential to verify that they are compatible with the meter that will be used to read them. There are three basic types of test strip: photometric; amperometric and visual. The first two are read by glucose meters and depend on the formation of a colored dye, or measuring the current produced, when glucose within the blood drop react with chemicals on the test strip. Visual test strips work on the same basis as photometric test strips but are less sensitive and are used when blood glucose levels are measured rarely.

The results of blood tests that indicate diabetes are interpreted against normal ranges (i.e. values for matched populations that do not have diabetes). Normally, blood glucose levels will be measured after the patient has not eaten for 8 hours prior to testing. A result greater than 126 mg/dl is indicative of diabetes. It is also possible to do a spot test; a result in excess of 200 mg/dl is suggestive of diabetes, if confirmed by other symptoms/history.


  1. Gestational Diabetes: Tests and Diagnosis. Mayo Clinic Staff. March 28, 2009.
  2. Diabetes Overview. NIH Publication No. 09–3873 November 2008. National Diabetes Information Clearinghouse:
  3. Medical Devices: Glucose Testing Devices. US Food & Drug Administration. Last Updated February 19, 2010.