What is a dangerous A1C level?

If you’ve recently been diagnosed with diabetes or pre-diabetes, your healthcare provider will likely recommend regular checks of your A1C levels. This is done with a hemoglobin A1C blood test, also known as the glycated hemoglobin, glycohemoglobin, or HbA1C test. By measuring how many red blood cells have glucose attached to them, the test is used to assess blood sugar levels over time. Providers use the test to screen for prediabetes and Type 2 diabetes and to assess how well-controlled the condition is in those who are already diagnosed (including those with Type 1 diabetes). 

The results of your A1C can be telling: The higher the A1C results, the higher the average blood sugar level. Very high and very low A1C results can be bad for your health for many reasons. Read on to see what you should know about your A1C test results.

What is a dangerous level of A1C?

A normal A1C range is 4% to 5.7%, according to the American Diabetes Association (ADA). Levels between 5.7% and 6.4% indicate prediabetes while 6.5% or higher indicates diabetes. 

When your A1C is consistently higher than 9%, you are at greater risk for developing long-term or chronic complications from poorly managed diabetes. Likewise, A1C levels that are consistently lower than 4% are associated with increased mortality. However, it’s fairly rare to have dangerously low A1C.

For people with diabetes, the medical condition is considered well-managed if A1C is 6.5% or lower for young adults, or between 7%-8% for older adults or those with other underlying health conditions or risk factors, according to the ADA.

When A1C levels are consistently very low, it can lead to diabetic coma or even death. Low blood sugar is referred to as hypoglycemia. “It can cause lightheadedness, sweating, palpitations, loss of consciousness, and seizures,” Dr. Makhija says. People with diabetes can experience low blood sugar if they are taking certain medications or using insulin injections. 

Stage 1 hypoglycemia occurs at an A1C level of 4% or lower, and stage 2 at an A1C level of 3.5% or lower, according to the ADA. 

A1C test measures are not used to diagnose Type 1 diabetes or gestational diabetes, but it can help manage these conditions.

7 complications of high A1C levels

Very high A1C levels indicate that a person’s diabetes is not well-managed. As A1C approaches 9%, the chances of having diabetes complications become much higher. Here are the seven most common health issues caused by dangerously high A1C levels.

1. Heart disease

High A1C levels raise the risk of cardiovascular disease because sustained high blood sugar harms the blood vessels and nerves that play a crucial role in the functioning of your heart. Luckily, research shows that lowering A1C levels with medication and lifestyle changes can reduce the risk of cardiovascular complications, such as myocardial infarctions (also known as heart attacks).

2. Kidney disease 

Hyperglycemia, or elevated blood sugar, damages the small blood vessels in the kidneys. When this happens, kidneys can’t clean the blood properly, which leads to kidney disease. “Other than uncontrolled high blood pressure, the primary reason for chronic kidney disease and advanced kidney failure … is poorly controlled diabetes,” says Chhaya Makhija, MD, an endocrinologist at Unified Endocrine & Diabetes Care in Fresno, California.

3. Nerve damage 

When your A1C levels are too high, it can harm the nerves in your body that help you feel things and move. When you develop nerve damage (also known as neuropathy) you might have strange sensations, such as tingling or pain in your hands, and feet, according to the U.S. Centers for Disease Control and Prevention (CDC). It can also affect how well you can control your muscles, and impact motor functions such as walking.

4. Slowed healing

High blood glucose levels can stiffen blood vessels and decrease circulation. The decreased blood flow makes it harder for the body to supply nutrients to wounds, leading to delayed or incomplete healing. “Foot ulcers and the need for surgical amputation … of a body part such as a finger, toe, hand, foot, arm, or leg are still common in cases of poorly controlled diabetes, which is often indicated by a long-standing high A1C test level,” Dr. Makhija says. 

5. Stroke

Having high A1C levels (greater than 6.8% to 7.0%) increases your risk of having a vascular event like a heart attack or stroke. “Stroke or cerebrovascular accidents commonly occur due to chronic conditions like uncontrolled high blood pressure, diabetes, high cholesterol, smoking, and alcohol use,” says Rasa Kazlauskaite, MD, an endocrinologist and an associate professor at Rush University Medical Center in Chicago. “People with Type 2 diabetes usually also have other metabolic conditions like hypertension and high cholesterol.” 

6. Memory loss

Research suggests that high blood sugar over a long duration increases your risk of developing memory issues. A 2013 meta-analysis found that people with uncontrolled diabetes faced a 73% higher risk of developing a form of dementia. Specifically, they had a 56% increased risk of Alzheimer’s dementia and a 127% increased risk of vascular dementia when compared to those without diabetes.

7. Eye problems (retinopathy)

When your A1C levels are consistently high, research shows it can cause retina damage, also known as retinopathy. This can make your vision fuzzy or unclear, almost as if you’re trying to see through a foggy lens. “In more severe cases, uncontrolled high A1C levels can even lead to the risk of blindness, where you may lose your ability to see entirely,” Dr. Kazlauskaite says.

How to improve your A1C levels

To reach your goal of keeping your A1C levels in the normal range, your treatment plan should include a combination of regular monitoring, lifestyle changes, and medication. Healthcare providers typically recommend the following four steps.

1. Monitor your diet. People with prediabetes or Type 2 diabetes should eat to keep blood sugar levels stable—without drastic highs or lows. That can mean opting for more whole foods such as vegetables, fruits, complex carbs, and lean protein while decreasing your intake of processed foods with lots of added sugar and simple carbohydrates, such as packaged baked goods, soda, or juice.
2. Regularly exercise. Losing 5%-7% of your body weight has been shown to reduce insulin resistance, which helps improve blood sugar control. You can kickstart weight loss by adding a post-meal walk, and work up to at least 150 minutes of physical activity a week. Creating and sticking to a regular workout routine can improve A1C numbers for those with prediabetes and Type 2 diabetes.
3. Monitor your blood sugar. A1C tests at your doctor’s visit don’t provide the whole picture. To manage Type 2 diabetes you’ll need to take regular blood sugar readings at home to make sure you’re meeting your target range. Your healthcare provider can help you establish how often you need to check it, but they may recommend it before meals, two hours after meals, and at bedtime. They may also recommend using a continuous glucose monitor. “[A CGM] helps you understand how your blood sugar levels change throughout the day, therefore, you can make the right adjustments,” Dr. Makhija says. Those with Type 2 diabetes will need to monitor this more closely than those with prediabetes, so be sure to talk with your provider or a diabetes care educator about how often is best for your condition.
4. Take your medication. If you are diagnosed with prediabetes and have other risk factors, your doctor may prescribe metformin to help lower your blood sugar levels and prevent Type 2 diabetes. If you are diagnosed with Type 2 diabetes, you may be prescribed the same or other diabetes medications such as Ozempic. While these medications will not cure the condition, they will help to manage it better and bring your A1C levels down. Every three months, you’ll have your A1C targets checked to see if they have been achieved and maintained. 

When to see your healthcare provider

If your A1C levels are in the acceptable range, your healthcare provider will likely only test them twice a year. But if your levels are 9% or higher, you will need to have them checked every three months. Your healthcare team will help you set an A1C goal and check to see if they have been achieved and maintained.

If you have prediabetes or diabetes, it’s important to see your provider regularly. But, if you’re experiencing any complications from your condition, such as nerve damage or eye problems, it’s even more important to schedule routine checkups. Working closely with your diabetes management team can help you improve your A1C and overall diabetes control.