What is A1C? Normal vs dangerous levels, and how to lower It

A1C is a blood test that measures your average blood sugar levels over the past two to three months. It plays a vital role in diagnosing and managing diabetes. This guide explains what A1C is, what counts as a normal or dangerous A1C level, and how you can lower your A1C through healthy lifestyle changes and, if needed, with medications prescribed by your healthcare provider.

What is A1C and what does it measure?

The A1C test (also known as the hemoglobin A1c, HbA1c, or glycated hemoglobin test) is a common blood test used to diagnose type 1 and type 2 diabetes and prediabetes. It's also used to monitor how well someone with diabetes is managing their blood sugar levels over time.

Glucose (sugar) in your bloodstream sticks to hemoglobin, the protein in your red blood cells that carries oxygen. The A1C test measures the percentage of your red blood cells that have glucose-coated hemoglobin. Those with high blood sugar have a higher percentage of blood cells that have glucose-coated hemoglobin compared to people with lower blood sugar levels.

Red blood cells live for about 3 months, so the A1C test provides an average picture of your blood sugar levels over the preceding 2 to 3 months. A higher A1C percentage means your average blood sugar levels have been higher during that period.

What is a normal and good A1C level?

An A1C level below 5.7% is considered normal for individuals without diabetes. This indicates that your average blood sugar levels over the past 2-3 months have been in a healthy range.

However, your A1C goal can depend on your age and medical conditions:

• For many adults diagnosed with diabetes, a common A1C target is below 7%. Achieving this level is generally considered "good" control and is associated with a significantly lower risk of developing long-term diabetes complications (like eye, kidney, and nerve damage).
• Older adults with diabetes may have an A1C goal of 7.5-8%, especially if they have multiple medical conditions and a life expectancy of less than 10 years. This goal can be even higher, such as 8 or 8.5%, for those with more complex conditions.
• Many children with type 1 diabetes have an A1C goal of below 7%, but this may be higher for children with severe low blood sugar or a short life expectancy. For example, some children with type 1 diabetes may have an A1C goal of below 8%.

A1C chart: How A1C matches average blood sugar

Studies show there is a direct, predictable relationship between the A1C percentage and average blood glucose levels over the preceding 2-3 months. As average blood glucose levels rise, more glucose attaches to hemoglobin, resulting in a higher A1C percentage.

Most people managing diabetes are familiar with blood glucose readings from their meters or continuous glucose monitors (CGMs), which are typically measured in milligrams per deciliter (mg/dL) in the United States or millimoles per liter (mmol/L) elsewhere. Translating the A1C percentage into an estimated average blood glucose measurement provides the result in these more familiar units. Below is an A1C chart that helps you translate your A1C into an average blood sugar level.

It is important to note that an average blood glucose level based on A1C is an estimate and individual results can vary. It reflects the central tendency of blood sugar over months but doesn't show the daily highs and lows that a person might experience. Someone could have the same estimated average blood glucose with very stable blood sugars or with significant swings between high and low readings. That's why regular self-monitoring of blood glucose is important for comprehensive diabetes management.

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What A1C level is considered dangerous?

While there isn't one single A1C number that flips a switch from "safe" to "dangerous," levels significantly above the recommended target indicate poor blood sugar control and dramatically increase the risk of serious diabetes-related complications.

Healthcare providers use the following A1C thresholds to diagnose prediabetes and diabetes:

• Prediabetes: (5.7–6.4%)
• Diabetes (6.5%+)

Persistently high average blood sugar levels (reflected in a high A1C) damage blood vessels and nerves throughout the body over time. This damage leads to serious complications, including:

• Eye problems (Retinopathy): Can lead to vision loss and blindness.
• Kidney disease (Nephropathy): Can lead to kidney failure requiring dialysis or transplant.
• Nerve damage (Neuropathy): Can cause pain, numbness, or tingling (especially in feet and hands), digestive issues, and other problems.
• Heart disease and stroke
• Foot problems: Nerve damage and poor circulation can lead to ulcers, infections, and potentially amputation.
• Dental problems: Increased risk of gum disease.

While any A1C level indicating diabetes (6.5% or higher) requires management to prevent complications, levels consistently above 8% signal a significantly elevated, dangerous risk, with urgency increasing dramatically for levels above 9% or 10%.

How can you lower your A1C?

Lowering your A1C level involves managing your average blood sugar over time. Some strategies that may help decrease your A1C include:

• Lifestyle changes, such as eating balanced meals and getting regular physical activity.
• Medications, like metformin or insulin, if needed.
• Weight management can help you lower your A1C naturally.
• Regular blood sugar monitoring to help you understand how foods and activities affect your levels.
• Stress management, since chronic stress can raise blood sugar levels.

You may be wondering how long it takes to lower your A1C. This is different for everyone, but by implementing these strategies consistently you can expect your A1C to improve by your next A1C test (typically in 3 months).