What diagnostic procedure measures the average amount of blood sugar for 3 months?

There are several ways to diagnose diabetes. Each way usually needs to be repeated on a second day to diagnose diabetes.

Testing should be carried out in a health care setting (such as your doctor’s office or a lab). If your doctor determines that your blood glucose (blood sugar) level is very high, or if you have classic symptoms of high blood glucose in addition to one positive test, your doctor may not require a second test to diagnose diabetes.

A1C

The A1C test measures your average blood glucose for the past two to three months. The advantages of being diagnosed this way are that you don't have to fast or drink anything.

  • Diabetes is diagnosed at an A1C of greater than or equal to 6.5%
     

Result

A1C

Normal less than 5.7%
Prediabetes 5.7% to 6.4%
Diabetes 6.5% or higher

Fasting Plasma Glucose (FPG)

This test checks your fasting blood glucose levels. Fasting means after not having anything to eat or drink (except water) for at least 8 hours before the test. This test is usually done first thing in the morning, before breakfast.

  • Diabetes is diagnosed at fasting blood glucose of greater than or equal to 126 mg/dl
     

Result

Fasting Plasma Glucose (FPG)

Normal less than 100 mg/dl
Prediabetes 100 mg/dl to 125 mg/dl
Diabetes 126 mg/dl or higher

Oral Glucose Tolerance Test (OGTT)

The OGTT is a two-hour test that checks your blood glucose levels before and two hours after you drink a special sweet drink. It tells the doctor how your body processes sugar.

  • Diabetes is diagnosed at two-hour blood glucose of greater than or equal to 200 mg/dl
     

Result

 Oral Glucose Tolerance Test (OGTT)

Normal  less than 140 mg/dl
Prediabetes  140 to 199 mg/dl
Diabetes  200 mg/dl or higher

Random (also called Casual) Plasma Glucose Test

This test is a blood check at any time of the day when you have severe diabetes symptoms.

  • Diabetes is diagnosed at blood glucose of greater than or equal to 200 mg/dl

What is Prediabetes?

Before people develop type 2 diabetes, they almost always have prediabetes—blood glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes.

Doctors sometimes refer to prediabetes as impaired glucose tolerance (IGT) or impaired fasting glucose (IFG), depending on what test was used when it was detected. This condition puts you at a higher risk for developing type 2 diabetes and cardiovascular disease.

Symptoms

There are no clear symptoms of prediabetes, so you may have it and not know it.

Some people with prediabetes may have some of the symptoms of diabetes or even problems from diabetes already. You usually find out that you have prediabetes when being tested for diabetes. 

If you have prediabetes, you should be checked for type 2 diabetes every one to two years.

Results indicating prediabetes are:

  • An A1C of 5.7–6.4%
  • Fasting blood glucose of 100–125 mg/dl
  • An OGTT two-hour blood glucose of 140–199 mg/dl

Preventing Type 2 Diabetes

You will not develop type 2 diabetes automatically if you have prediabetes. For some people with prediabetes, early treatment can actually return blood glucose levels to the normal range.

Research shows that you can lower your risk for type 2 diabetes by 58% by:

  • Losing 7% of your body weight (or 15 pounds if you weigh 200 pounds)
  • Exercising moderately (such as brisk walking) 30 minutes a day, five days a week

Don't worry if you can't get to your ideal body weight. Losing even 10 to 15 pounds can make a huge difference. 

Hemoglobin A1c (HbA1c) Test for Diabetes

What Is an A1c Test?

The hemoglobin A1c test tells you your average level of blood sugar over the past 2 to 3 months. It's also called HbA1c, glycated hemoglobin test, and glycohemoglobin. It’s a lot like a baseball player's season batting average. A single game doesn't tell you how a player is performing in their career. And 1 day's test results don't give you the complete picture of how your treatment is working.

People who have diabetes need this test regularly to see if their levels are staying within range. It can tell if you need to adjust your diabetes medicines. The A1c test is also used to diagnose diabetes.

What Is Hemoglobin?

Hemoglobin is a protein found in red blood cells. It gives blood its red color, and its job is to carry oxygen throughout your body.

How the Test Works

The sugar in your blood is called glucose. When glucose builds up in your blood, it binds to the hemoglobin in your red blood cells. The A1c test measures how much glucose is bound.

Red blood cells live for about 3 months, so the test shows the average level of glucose in your blood for the past 3 months.

If your glucose levels have been high over recent weeks, your hemoglobin A1c test will be higher.

What diagnostic procedure measures the average amount of blood sugar for 3 months?

What's a Normal Hemoglobin A1c Test?

For people without diabetes, the normal range for the hemoglobin A1c level is between 4% and 5.6%. Hemoglobin A1c levels between 5.7% and 6.4% mean you have prediabetes and a higher chance of getting diabetes. Levels of 6.5% or higher mean you have diabetes.

 
What diagnostic procedure measures the average amount of blood sugar for 3 months?

Setting Goals for A1c Levels

The target A1c level for people with diabetes is usually less than 7%. The higher the hemoglobin A1c, the higher your risk of having complications related to diabetes. Someone who has had untreated diabetes for a long time might have a level above 8%.

If you have diabetes and your level is above your target, your doctor may change your treatment plan to get your level down.

A combination of diet, exercise, and medication can bring your levels down.

People with diabetes should have an A1c test every 3 months to make sure their blood sugar is in their target range. If your diabetes is under good control, you may be able to wait longer between the blood tests. But experts recommend checking at least two times a year.

People with diseases affecting hemoglobin, such as anemia, may get misleading results with this test. Other things that can affect the results of the hemoglobin A1c include supplements such as vitamins C and E and high cholesterol levels. Kidney disease and liver disease may also affect the test.

How Often Do You Need the Test?

Your doctor probably will have you take the A1c test as soon as you’re diagnosed with diabetes. You’ll also have the test if your doctor thinks you may get diabetes. The test will set a baseline level so you can see how well you’re controlling your blood sugar.

How often you’ll need the test after that depends on several things, like:

  • The type of diabetes you have
  • Your blood sugar control
  • Your treatment plan

You’ll probably get tested once a year if you have prediabetes, which means you have a strong chance of developing diabetes.

You may get tested twice each year if you have type 2 diabetes, you don't use insulin, and your blood sugar level is usually in your target range.

You could get it three or four times each year if you have type 1 diabetes.

You may also need the test more often if your diabetes plan changes or if you start a new medicine.

It’s not a fasting test. You can take it any time of day, before or after eating. 

People with diseases affecting hemoglobin, such as anemia, may get misleading results with this test. Other things that can affect the results of the hemoglobin A1c include supplements, such as vitamins C and E, and high cholesterol levels. Kidney disease and liver disease may also affect the test.

What is the average blood sugar level for 3 months?

HbA1c is your average blood glucose (sugar) levels for the last two to three months. If you have diabetes, an ideal HbA1c level is 48mmol/mol (6.5%) or below. If you're at risk of developing type 2 diabetes, your target HbA1c level should be below 42mmol/mol (6%).

What test measures average blood glucose over a 2 3 month period?

An A1C test result reflects your average blood sugar level for the past two to three months. Specifically, the A1C test measures what percentage of hemoglobin proteins in your blood are coated with sugar (glycated). Hemoglobin proteins in red blood cells transport oxygen.

Which method is used for estimation of blood sugar?

There are three basic approaches to the laboratory measurement of blood glucose concentration: reducing methods, condensation methods, and enzymatic methods.