Dangerous A1C Levels and Risks

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 is an A1C between 5.7 and 6.4%.

Diabetes is an A1C of 6.5% or higher.

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, such as retinopathy, that can lead to vision loss and blindness.
Kidney disease or nephropathy that can lead to kidney failure requiring dialysis or transplant.

Nerve damage or neuropathy, which can cause pain, numbness, or tingling (especially in feet and hands), digestive issues, and other problems.

Heart disease and stroke.

Foot problems, such as nerve damage and poor circulation can lead to ulcers, infections, and potentially amputation.

Dental problems, such as 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%.