Tests for Diabetes
If you have certain risk factors or symptoms, your health care provider may decide to test you for diabetes.
Those diagnosed with diabetes, which is diagnosed through blood testing, may be asked to test their blood sugar regularly. Home blood sugar testing can help reveal if your treatment plan is working. Here you'll learn about blood tests used to diagnose and monitor diabetes.
Blood tests used to diagnose diabetes and prediabetes
There are several different blood tests used to diagnose diabetes. Each method usually needs to be repeated on a different day to diagnose diabetes. If your health care provider determines that your blood glucose (sugar) level is very high, or if you have symptoms of high blood sugar and a positive test result, you may not have a second test for a type 2 diabetes diagnosis.
These blood tests can also tell if you have prediabetes. What does pre diabetic mean? Prediabetes means that your blood sugar is higher than normal blood glucose levels, but not high enough for a diabetes diagnosis. Prediabetes is a warning sign of diabetes, and there are no clear symptoms of prediabetes. People with prediabetes are at high risk for developing diabetes, but diabetes can often be prevented with lifestyle changes, such as losing weight, eating nutritious foods and getting regular exercise. If you have prediabetes, your health care provider will likely test you for type 2 diabetes every one to two years. Various blood tests can be used to diagnose diabetes:
Fasting plasma glucose test
This test measures your fasting blood glucose levels after you haven't had anything to eat or drink for at least eight hours.
| Fasting plasma glucose reading | Result |
|---|---|
| Less than 100 mg/ dL | Normal |
| 100–125 mg/dL | Prediabetes |
| 126 mg/dL or higher | Diabetes |
Hemoglobin A1C test
What does A1C measure? It reflects your average blood sugar over a two to three month period. Hemoglobin is part of red blood cells that carries oxygen to the cells, and glucose attaches to the hemoglobin. The higher the amount of glucose in your bloodstream, the more glucose will attach to the hemoglobin. The A1C test, which does not require fasting, is reported as a percentage and measures the amount of hemoglobin with attached glucose. This test can be used to diagnose type 2 diabetes and prediabetes.
| A1C levels | Result |
|---|---|
| Less than 5.7% | Normal hemoglobin A1C level |
| 5.7-6.4% | Prediabetes hemoglobin A1C level |
| 6.5% or higher | Diabetes or high hemoglobin A1C level |
If you already have diabetes, an A1C diabetes test can also tell how well your blood sugar is under control. It can also guide your health care provider to make adjustments to your treatment plan. This test result allows your health care provider to see what your blood sugar has been over the past three months, and make adjustments to your treatment plan if needed. Your A1C target is often personalized and changes over time. Ask your health care provider what A1C goal is right for you. Studies show that some people can reduce their risk of diabetes-related complications if they keep their A1C below 7%. It's recommended that people with diabetes have their A1C measured at least two times per year.
Oral glucose tolerance test
This test reveals how your body processes glucose. It measures how quickly your blood sugar returns to normal after fasting and then drinking a sweetened beverage containing 75 grams of glucose. You'll have your blood sugar levels checked before and two hours after drinking the liquid.
| Oral glucose tolerance reading two hours after drinking 75 grams of glucose | Result |
|---|---|
| Less than 140 mg/ dL | Normal |
| 140–199 mg/dL | Prediabetes |
| 200 mg/dL or higher | Diabetes |
Pregnant women receive a modified version of the glucose tolerance test to check for gestational diabetes:
- One step approach: This test involves fasting for at least eight hours and then drinking 75 grams of glucose. You'll have your blood sugar levels checked at fasting, at one hour after drinking the liquid and at two hours after drinking the liquid. Your provider will likely diagnose you with gestational diabetes if your blood sugar meets or exceeds one or more of these levels:
- Fasting: 92 mg/dL
- One hour after drinking 75g of glucose: 180mg/dL
- Two hours after drinking 75g of glucose: 153mg/dL
- Two step approach: It doesn't require fasting and is often done in two steps to confirm a diagnosis. First, you'll be asked to drink a glucose-containing liquid. One hour after consuming the beverage, your blood will be drawn. If your blood sugar reading is 130 mg/dL or higher, your health care provider will likely have you take three-hour oral glucose tolerance test at another time before making a gestational diabetes diagnosis.
Random blood glucose test
This test doesn't require fasting and can be done at any time. A blood sugar reading higher than 200 mg/dL indicates diabetes.
Home blood glucose testing
After you're diagnosed with diabetes, your health care provider may tell you to test your blood sugar regularly at home. Self-testing can help you know if your treatment plan is working. Your diabetes health care team will give you specific advice on how to keep your blood sugar levels in a healthy range.
Blood glucose meters or glucometers are devices that allow you to test your blood sugar at home. Most meters require you to prick your skin with a lancing device with a needle to draw blood. You place a drop of blood onto a test strip that's inserted in the meter. Then the meter displays your current blood sugar level. This is the most common way to monitor blood glucose levels at home. There's also another method of testing blood sugar levels using a device called a continuous glucose monitor. A continuous glucose monitor uses a small sensor that's placed under your skin, often in your abdomen or arm. The sensor measures your blood sugar at frequent intervals and sends the results to a device you wear on your body. The device produces a digital readout, so you can know your blood sugar levels in real time and get a better sense of what is happening with your blood sugar throughout the day.
If I have diabetes what should my blood sugar be?
If you're wondering what is normal blood sugar for a diabetic, know that this specific range varies between people. Your health care provider will tell you what is a good blood sugar level for you. According to the American Diabetes Association, general goal diabetic blood sugar ranges are as follows. Still, you should always strive to meet the diabetes sugar level targets your health care provider sets for you.
| Time of blood sugar test | Diabetes blood sugar reading |
|---|---|
| Fasting or before breakfast | 80–130 mg/ dL |
| Before lunch, dinner or a snack | 80–130 mg/ dL |
| One to two hours after beginning a meal | < 180 mg/ dL |
High and low blood sugar
Sometimes your blood sugar may not be in your target range. Your health care provider can let you know what readings are considered high and low blood sugar levels for you. It's important to know how to recognize the symptoms of high and low blood sugar. Ask your health care provider what actions you should take if your blood sugar is too high or too low.
Hyperglycemia is the medical term for high blood sugar. Symptoms of high blood sugar include:
- High blood sugar readings
- High levels of sugar in the urine
- Increased thirst
- Frequent urination
Hypoglycemia (low blood sugar) occurs when your blood glucose drops below normal blood sugar levels. For many people with diabetes, this means below 70 mg/ dL, but your health care provider may have a different threshold for you. Symptoms of low blood sugar can come on very quickly, can vary between people and depend on how low you blood sugar falls. Severe hypoglycemia is when your blood sugar falls so low you're unable to treat yourself. This condition is an emergency, and can lead to a diabetic seizure and brain damage.
Mild-to-moderate low blood sugar symptoms include:
- Shakiness
- Dizziness or lightheadedness
- Irritability
- Nervousness
- Sweating
- Hunger
- Headache
- Blurred vision
- Sleepiness
- Confusion or disorientation
- Weakness
- Trouble concentrating
- Argumentative
- Changes in personality
- Fast or irregular heartbeat
- Pale complexion
Symptoms of severe low blood sugar include:
- Convulsions (jerky movements) or seizures
- Not being able to eat or drink
- Loss of consciousness
In summary, there are a host of blood tests used to diagnose diabetes and help guide your treatment plan. If you have diabetes, work closely with your healthcare provider to learn your target blood glucose range, and monitor your blood sugar as directed. Then follow your treatment plan exactly as prescribed so you can keep your blood sugar under control.
Reviewed on December 18, 2020
Sources
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