What Happens When A1C Is Too High?

A1C is a blood test that determines the body's average blood sugar level over the past two to three months. A1C is also referred to as the hemoglobin A1C, HbA1c, glycated hemoglobin, or glycohemoglobin test. In the body, a protein called hemoglobin transports oxygen and nutrients throughout the body. It can pick up glucose on the way, and glucose will bind to the hemoglobin, which then becomes a glycated hemoglobin. The higher the glucose level in your bloodstream, the more glucose will attach to the hemoglobin. The A1C test measures the amount of hemoglobin with attached glucose.

This test is used frequently to diagnose prediabetes and diabetes, as well as to monitor treatment plans for people with diabetes. Experts have determined healthy, prediabetes, and type 2 diabetes ranges for A1C, and knowing your A1C level can help you make adjustments to treatments and lifestyle.

Female nurse is taking blood of a senior patient at hospital

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A1C Ranges and What They Mean

An A1C result is presented as a percentage, which reflects the percentage of glucose and hemoglobin that are bound together. For example, the A1C level where there are five glycated hemoglobin out of 100 hemoglobin would be 5%.

The A1C ranges for normal, prediabetes, and diabetes are as follows:

  • Normal: Less than 5.7%
  • Prediabetes: 5.7% to 6.4%
  • Diabetes: 6.5% or higher

The higher the A1C, the higher your blood glucose levels have been. If your A1C falls into the range of prediabetes, you should talk to your healthcare provider to determine the best way to prevent type 2 diabetes because prediabetes is a known risk factor of type 2 diabetes. In general, within the prediabetes range, the higher the A1C, the greater the risk of diabetes.

The A1C test should not be used to diagnose type 1 diabetes, gestational diabetes, or cystic fibrosis-related diabetes.

What Happens When A1C Is Too High

A high A1C level should not be ignored. Studies show a direct correlation between high A1C and severe diabetes complications. An A1C level above 7% means someone is at an increased risk of complications from diabetes, which should prompt a person to make sure they have a plan in place to manage their blood sugar levels and decrease this risk. If these strategies are already in place, an increase in A1C may show that they need to be tweaked. 

Several factors can falsely increase or decrease your A1C result, including:

  • Kidney failure, liver disease, or severe anemia
  • Being of African, Mediterranean, or Southeast Asian descent
  • Certain blood disorders (such as sickle cell anemia or thalassemia)
  • Certain medicines, including opioids and some HIV medications
  • Blood loss or blood transfusions
  • Early or late pregnancy

If better management doesn't take place, high blood sugar can lead to serious complications like heart disease, stroke, vision loss, nerve damage, kidney disease, and gum disease. Short-term problems to look out for include hypoglycemia and hyperglycemia.

Heart Disease and Stroke

People living with diabetes have high blood sugar, and over time this can damage the blood vessels and nerves that control the heart, leading to heart disease. It has been found that people with diabetes tend to develop heart disease at a younger age than people without diabetes. Also, the longer you have diabetes, the more likely you are to have heart disease.

The most common type of heart disease is coronary artery disease, which is caused by the buildup of plaque in the walls of the coronary arteries, the blood vessels that supply oxygen and blood to the heart. Plaque is made of cholesterol deposits, which make the inside of arteries narrow and decrease blood flow. This process is called atherosclerosis, or hardening of the arteries. Decreased blood flow to the heart can cause a heart attack.

Decreased blood flow to the brain can also cause a stroke. Patients with diabetes are particularly at a significantly higher risk of stroke and have a higher mortality.

Those who have diabetes are also more likely to have other conditions that raise the risk for heart disease, including:

  • High blood pressure: This increases the force of blood through your arteries and can damage artery walls.
  • Too much low-density lipoprotein (LDL) cholesterol: Also, known as bad cholesterol, this can lead to the formation of plaque on damaged artery walls.
  • High triglycerides: This combined with a low HDL cholesterol or high LDL cholesterol is thought to contribute to hardening of the arteries.

People with diabetes are also more likely to have heart failure, which is when your heart can’t pump blood well. 


Diabetes can also cause damage to your eyes that can lead to poor vision and vision loss. Eye problems that can affect people with diabetes are referred to as diabetic eye disease, which include diabetic retinopathy, diabetic macular edema (fluid retention in the retina), cataracts, and glaucoma. However, people with diabetes can take steps to prevent diabetes eye disease by taking care of their diabetes.

If your blood glucose stays high over time, it can damage the tiny blood vessels in the back of your eyes. This damage can begin during prediabetes. Damaged blood vessels may leak fluid and cause swelling. New, weak blood vessels may also begin to grow. These blood vessels can bleed into the middle part of the eye, lead to scarring, or cause dangerously high pressure inside your eye.

Diabetic retinopathy is the most common cause of vision loss in people with diabetes. Finding and treating diabetic retinopathy early can reduce the risk of blindness by 95%.

There are often no warning signs when damage to your eyes first develops. A full, dilated eye exam helps your healthcare provider find and treat eye problems early—before much vision loss can occur.

Adults with type 1 diabetes should get a dilated eye exam within five years of being diagnosed, and then every year after that. For adults with type 2 diabetes, they should have an eye exam soon after diagnosis and a dilated eye exam every year after. However, an exam every one to two years may be considered after one or more normal eye exams.

Nerve Damage

Nerve damage caused by diabetes is called diabetic neuropathy. High blood sugar damages your nerves, and these nerves may stop sending messages to different parts of your body. Nerve damage can cause problems ranging from mild numbness to pain. Half of all people with diabetes have nerve damage. 

There are several types of neuropathy:

  • Peripheral nerve damage: This type of damage affects your hands, feet, legs, and arms, and it’s the most common type of nerve damage for people with diabetes. It generally starts in the feet—usually in both feet at once.
  • Autonomic nerve damage: This affects your heart, bladder, stomach, intestines, sex organs, or eyes.
  • Proximal nerve damage: This affects nerves in the thighs, hips, buttocks, or legs. It can also affect the stomach and chest area.
  • Focal nerve damage: This affects single nerves, most often in your hand, head, torso, or leg. 

People with diabetes should be looking out for symptoms of nerve damage by recognizing new symptoms related to pain, numbness, or new problems with continence or bowel control. Like with other complications, keeping your blood sugar as close to your target range as possible is the best way to help prevent or delay nerve damage.

Kidney Disease

People with diabetes could also get diabetic kidney disease. About one out of three adults with diabetes has kidney disease. High blood glucose can damage the blood vessels in your kidneys. When that happens, they don’t work as well. Many people with diabetes also develop high blood pressure, which can also damage the kidneys.

Gum Disease

Diabetes doesn't only lead to high blood sugar levels. People with diabetes also have sugars in saliva, which come in contact with the mouth. Their teeth and gums are therefore exposed to more sugars, which helps germs and plaque grow, irritating the gums and causing gum disease.

In addition to gum disease, your jaw and tongue, and other mouth tissue can be affected. The most common gum disease and other mouth problems that people with diabetes have include:

  • Gingivitis (unhealthy or inflamed gums)
  • Periodontitis
  • Thrush (oral yeast infection)
  • Xerostomia (dry mouth)
  • Oral burning

Some of the first signs of gum disease are swollen, tender, or bleeding gums. Sometimes you may not have any signs of gum disease. You may not know you have it until you have serious damage. Your best defense is to see your dentist twice a year for a cleaning and checkup.

Lowering A1C

While diabetes complications are severe, there are ways to manage blood sugar to lower your A1C levels and prevent them. With the help of medical professionals, a treatment plan, which includes medication and lifestyle changes, will help lower your levels and avoid complications.

Healthy Eating and Meal Tracking

Your diet has a huge impact on the way your body produces and uses blood sugar. In order to maintain a healthy blood sugar level and therefore lower A1C, healthy eating and meal tracking help. Meal tracking helps you plan ahead for healthy options as well as look back on what might have spiked your blood sugar.

A few healthy snacks to lower your A1C include:

  • Berries
  • Nuts
  • Eggs
  • Yogurt
  • Apples

Stress Relief Techniques

Managing stress is crucial to staying healthy in general, and can particularly help people with diabetes.

Studies have shown that acute stress can increase glucose production and interfere with glucose utilization. This means better control of stress can have a positive impact on blood sugar levels.

Some stress relief techniques include:

  • Yoga
  • Journaling
  • Meditating
  • Talk therapy

Stay Active

Exercise helps people with diabetes for a variety of reasons, including weight loss and stress relief, but it also directly affects blood sugar levels. When you exercise, your muscles need and use sugar, which lowers the levels in the blood. Research has shown that long-term regular physical activity training had positive effects on glycemic control and body composition among patients with type 2 diabetes. It also promoted cardiovascular fitness among these patients.

The more exercise, the greater A1C reduction. Most people with diabetes should aim for at least 150 minutes of moderate-intensity exercise each week.

Medication and Regular Monitoring

A1C is an important tool for managing diabetes, but it doesn’t replace regular blood sugar testing at home. Blood sugar goes up and down throughout the day and night, which isn’t captured by your A1C. Two people can have the same A1C, one with steady blood sugar levels and the other with high and low swings.

If you’re reaching your A1C goal but having symptoms of highs or lows, check your blood sugar more often and at different times of day. Keep track and share the results with your healthcare provider so you can make changes to your treatment plan and medications if needed.

A Word From Verywell

The A1C blood test is just one of many tools to check and monitor blood sugar. A1C is an average of your blood sugar level over 90 days, so healthcare providers will likely recommend checking levels of blood sugar between A1C tests if blood sugar isn't managed. Keeping track of your blood sugar regularly can help you identify things that affect your blood sugar level and tweak your management plan. Managing diabetes is your best defense against the various complications that this condition can cause. Discuss concerns and new symptoms with your healthcare provider to make sure your treatment plan addresses your needs.

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