What Does It Mean When Your Hemoglobin A1C Is High?

Medically Reviewed on 1/4/2023

How does the hemoglobin A1C test work?

The hemoglobin A1C is a test that measures your average blood sugar for the past three months. If your hemoglobin A1C is high it could mean that you are prediabetic or diabetic.
The hemoglobin A1C is a test that measures your average blood sugar for the past three months. If your hemoglobin A1C is high it could mean that you are prediabetic or diabetic.

The hemoglobin A1C is a test that measures your average blood sugar for the past three months. This test goes by other names, including glycated hemoglobin, glycosylated hemoglobin, or HbA1c. 

If you have diabetes, your doctor may use the A1C to check how well you are controlling your blood sugar. A high hemoglobin A1C may mean that your treatment plan needs revision. The A1C is also used to diagnose diabetes or prediabetes.

Hemoglobin is the protein that gives red blood cells their color. Its job is to carry oxygen to all the cells in your body. As red blood cells travel around the body, glucose in the bloodstream attaches itself to the hemoglobin. The A1C test measures how much glucose is attached. Since red blood cells live around three months, the A1C test shows how high your blood sugar has been for the past three months. 

A1C as a screening test

Combined with other indicators, the A1C can screen for both type 1 and type 2 diabetes. Type 1 diabetes usually develops during childhood or young adulthood. No one is certain what causes it. Type 2 usually develops later and has certain risk factors. You are more likely to develop type 2 diabetes if you:

  • Are over 45 years of age
  • Are overweight
  • Lead a sedentary lifestyle  
  • Have a parent or sibling with diabetes
  • Had diabetes during pregnancy or had a baby weighing over 9 pounds

If you are being screened for diabetes, your A1C results will fall into one of three categories:

  • Less than 5.7%: normal, not diabetic
  • 5.7% to 6.4%: prediabetic
  • 6.5% or higher: diabetic

A1C as a monitoring test

If you have already been diagnosed with diabetes, your doctor may use the hemoglobin A1C test to monitor your blood glucose levels. A result of 7% or less usually means that you are controlling your diabetes. 

Although less than 7% is a common goal, a higher reading may be better for some people. If you are prone to low blood sugar, also known as hypoglycemia, your doctor may prefer an A1C between 7% and 8%. A higher goal may also be better for those who have had diabetes for a long time or who have complications of the disease.  

Difference between A1C and blood glucose

If you have diabetes, you may check your blood sugar at home. This test differs from the A1C. When you test your blood glucose, you are checking your blood sugar level at one moment in time. Your test result will reflect how long it has been since you ate something and the type of food you ate.

Home glucose testing gives you and your doctor information that the A1C does not. The A1C gives a blood sugar average but does not show whether your levels are steady or whether they go very high and very low. Your doctor needs both types of tests to understand how well you are controlling your blood sugar.

How accurate is the A1C?

Your doctor can do an A1C test using a blood sample from a finger prick. Called a point-of-care test, this test can be processed quickly. Your doctor may instead choose to take a larger blood sample and send it to a lab for processing. The results of the lab test may be slightly more accurate. 

If you have recently had a blood transfusion, your A1C may not be accurate. Other health conditions can affect the red blood cells and result in inaccurate A1C results. These include:

Can you have a high A1C level and not have diabetes?

Yes. A high A1C level does not necessarily mean that you have diabetes. High A1C can be an early warning sign of prediabetes, for example. Still, the higher your A1C, the greater your risk is of developing type 2 diabetes, according to the CDC. The best way to know for sure if you have diabetes is to get the opinion of your doctor.

What causes high A1C besides diabetes?

Although a high A1C reading is often a sign of type-2 diabetes, it can be affected by other things that influence your hemoglobin levels. These could include:

Why the A1C is important

If you have diabetes, a high hemoglobin A1C means that you are more likely to experience complications. Some complications are serious. They include:

Screening for diabetes is also important. Those with an A1C greater than 6% are at high risk of developing diabetes in the next 5 years. Identifying them is critical. Research shows that two interventions can lower their chances of developing diabetes. Lifestyle changes can reduce their risk by 50%. Using the drug metformin can reduce it by 30%. 

What to do about a high A1C

After a high hemoglobin A1C, you and your doctor can work together to lower your numbers and reduce your risks. Your doctor may recommend a three-pronged approach combining education, diet, and exercise. Also, you may need to lose weight if you are overweight.

If you have type 1 diabetes, you will need treatment with drugs. Many of those with type 2 diabetes will require drug therapy as well. 


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What foods should I avoid if my A1C is high?

Some foods are more likely to raise your A1C blood sugar average over time. If you eat these foods consistently, your A1C is likely to stay high or go higher:

  • Foods high in flour, including breads, rolls, and biscuits
  • Pasta
  • Rice
  • Potatoes
  • Soda

What foods can bring my A1C down?

You can help lower your A1C blood sugar average by consistently eating the following foods:

  • Beans and lentils
  • Berries
  • Kale
  • Oats/Oat Bran
  • Tomatoes
  • Cucumbers
  • Whole grain pasta
  • Seafood
  • Plain yogurt

Besides medication, what are other ways to lower my A1C naturally?

Watching your diet, including portion sizes and calories, can help you naturally reduce your A1C blood sugar average over time. Avoid foods that contribute to high blood sugar, especially sugary sodas, juice, and fruit drinks. Be conscious of healthy carb choices, like preferring beans and lentils over potatoes and rice. And get active! Getting regular, daily exercise is an essential component of overall health and helps promote lower blood sugar.

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Medically Reviewed on 1/4/2023

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