How to Test for Diabetes

diabetest test

There are several ways to test a person for diabetes.  Diabetes testing can be done on anyone who has symptoms of diabetes, such as increased thirst, increased frequency of urination, poorly healing wounds, or unexplained weight loss.

Testing for diabetes can also be done on people who have risk factors for diabetes but have no symptoms.  According to the American Diabetes Association (ADA), some people should be screened for diabetes in the absence of any symptoms.  These people include the following:

1. People who are 45 years of age or older.

These individuals need a first blood sugar screening at around age 45 and should have the screening repeated every 3 years or so for the rest of their lives.

2. People with a body mass index (BMI) greater than 25, independent of age

If a person is considered to be:

  • overweight or obese, or
  • have other risk factors of diabetes, such as hypertension, polycystic ovarian syndrome, history of gestational diabetes, lack of exercise, having a baby weighing more than 9 pounds, having high cholesterol levels, having heart disease in the past, or
  • having a first degree relative who had type 2 diabetes.

are you diabetic

Tests for Type 1 Diabetes, Type 2 Diabetes, and Prediabetes

There are several ways to show that a person has diabetes or is at risk for diabetes.  The usual tests for diabetic screening include the following:

Hemoglobin A1c Level.

This is also referred to as a glycated hemoglobin level. It is a measure of how “sugar-coated” the hemoglobin is in the red blood cells of the body. Because red blood cells survive for about 120 days, the test measures the average blood sugar level over the past three months. The test is measured in percentages.  The higher the blood glucose level is, the more sugar-coated will be the hemoglobin and the higher the hemoglobin A1c level is.  A normal test is a Hgb A1c level of below 5.7.  If the hemoglobin A1c level is 6.5 percent or greater and this is shown in a follow-up test, it indicates that an individual has diabetes.  Prediabetes Is when the hemoglobin A1c level is 5.7 to 6.4 percent.  People with prediabetes often go on to having full-blown diabetes if they don’t lose weight or eat a low sugar diet.

If you are pregnant or have a disease with a variant of hemoglobin, such as sickle cell anemia, the hemoglobin A1c level will be inaccurate so that other tests must be done to determine if diabetes may be present.
a1c level test

Random Blood Glucose Testing.

Diabetes can be diagnosed by just having a random blood sugar test taken. It is done any time of the day and is independent of when a person last had a meal.  Any blood glucose level of more than 200 mg/dL is indicative of diabetes (11.1 millimoles per liter) indicates that you probably have diabetes and need treatment in order to prevent complications.

Fasting blood sugar testing.

Diabetes can be diagnosed by checking a fasting blood sugar test. The test is done in the morning after you have been fasting since the night before.  Any blood glucose level of less than 100 milligrams per deciliter is considered a normal blood glucose test.  Any fasting blood glucose test of between 100 and 124 milligrams per deciliter indicates that you have prediabetes and will need more careful monitoring to see if you become diabetic. Any blood sugar level of 125 milligrams per deciliter on a fasting basis is considered to be diabetes.  Usually, the diagnosis is made after two such fasting tests have been considered high.

Oral glucose tolerance test.

In this test, the individual fasts overnight and has the test beginning in the morning. First, a fasting blood glucose level is drawn.  Then the person drinks a sugary beverage that contains glucose in it.  The blood is tested every one-half to one hour for up to 3 hours.  Any blood glucose reading of less than 140 milligrams per deciliter is considered normal.  Any blood sugar reading of between 140 and 199 milligrams per deciliter is considered to be prediabetes.  Any blood glucose reading of greater than 200 milligrams per deciliter on any of the measurements means that the person has diabetes.

If it is suspected that the person has type 1 diabetes, the urine is checked for ketones.  Ketones are a byproduct of the metabolism of fat and muscle tissue because there is no insulin around to use for cellular energy.  If type 1 diabetes is suspected, the doctor may also check for autoantibodies to pancreatic tissue, which is a sure sign that the person has type 1 diabetes.

Testing for Gestational Diabetes

Every woman who is pregnant is screened for gestational diabetes at around 24 weeks’ gestation.  Women are tested earlier than that if they have a higher risk of having gestational diabetes due to obesity, a family history of diabetes, or a previous infant who weighed over 9 pounds.

Even if a woman has no risk factors for diabetes, she is tested for gestational diabetes at 24 weeks.  The test usually involves what is known as a one-hour glucose tolerance test.  In this test, the individual doesn’t have to be fasting.  A 50-gram load of glucose is given by drinking a sugary beverage.  After that, the blood sugar level is measured.  If the blood glucose level is 140 milligrams per deciliter on that test, it may mean that she has gestational diabetes.  Follow up tests are done to see if the individual has gestational diabetes or not.  The follow-up test usually involves having a 3-hour glucose tolerance test.

A 3-hour glucose tolerance test is done on suspected gestational diabetic women.  This is done exactly in the same way as when a person isn’t pregnant.  The woman is fasting and drinks a 100-gram glucose load by drinking a sugary beverage.  Several blood sugar levels are measured and if any of these are high, the woman is considered to have gestational diabetes.
random blood gucose testing


Tests and Diagnosis. Accessed 5/16/16.

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