A normal HbA1c for adults of any age is below 5.7%, but average levels naturally rise with age. People in their 20s and 30s without diabetes typically average around 5.1%, while those over 60 tend to average closer to 5.5%. These shifts are modest, and the clinical cutoffs for prediabetes (5.7% to 6.4%) and diabetes (6.5% or above) remain the same regardless of age.
What HbA1c Measures
HbA1c reflects your average blood sugar over the past two to three months. It works by measuring how much sugar has attached to your red blood cells. Because red blood cells live about 120 days, the test captures a rolling window of blood sugar exposure rather than a single snapshot. This makes it more stable than a finger-prick glucose reading, which can swing depending on what you ate an hour ago.
Average HbA1c by Age Group
Large population studies of adults without diabetes show a clear, gradual upward trend in HbA1c as people age. Data from national surveys between 1999 and 2006 found the following averages:
- Ages 20 to 39: 5.1%
- Ages 40 to 59: 5.4%
- Ages 60 to 69: 5.5%
- Ages 70 and older: 5.5%
Research across different populations has confirmed this pattern, estimating that HbA1c rises by roughly 0.01 to 0.02 percentage points per year of life. So a healthy 30-year-old and a healthy 70-year-old might differ by about 0.4 to 0.5 percentage points, even with similar diets and activity levels. The proportion of people with an HbA1c above 6% also increases considerably with age, even among those never diagnosed with diabetes.
Why HbA1c Rises With Age
The body becomes less efficient at processing blood sugar as it ages. Insulin sensitivity tends to decline, meaning cells don’t respond to insulin as effectively. Kidney function gradually slows, which can alter how glucose is filtered. Muscle mass, which absorbs a significant share of blood sugar after meals, typically decreases over the decades. None of these changes automatically mean diabetes, but together they nudge average blood sugar slightly higher.
Standard Diagnostic Cutoffs
Despite the natural age-related rise, clinical thresholds do not change by decade. The CDC uses the same ranges for all adults:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
This means a 65-year-old with an HbA1c of 5.8% would technically fall in the prediabetes range, even though the population average for their age group is only slightly lower. Context matters. Your doctor will weigh your result alongside fasting glucose, body weight, family history, and other risk factors before making a diagnosis.
Targets for People Already Managing Diabetes
If you’ve been diagnosed with diabetes, the goal shifts from “normal” to a safe, achievable target. The American Diabetes Association recommends an HbA1c below 7% for most nonpregnant adults. Some people can safely aim lower, below 6.5%, if they can reach that level without frequent drops in blood sugar or other side effects. For others, particularly older adults with multiple health conditions or limited life expectancy, a more relaxed target may be more appropriate.
The reasoning is straightforward: pushing HbA1c too low with medication can cause blood sugar to crash, especially in people taking insulin. Older adults are more vulnerable to these crashes because of changes in kidney function, medication metabolism, and the body’s ability to recognize and recover from low blood sugar. That said, recent research found that sustaining an HbA1c below 7% on insulin did not significantly increase the risk of falls or fractures in older adults, though severe individual episodes of low blood sugar were still linked to fall risk.
HbA1c Targets for Children and Teens
For children and adolescents with type 1 diabetes, the ADA recommends an HbA1c below 7%. Kids who use continuous glucose monitors or advanced insulin pumps can sometimes aim for below 6.5% safely. For children with type 2 diabetes, which carries a higher risk of complications at a young age, the recommended target is below 6.5%.
These goals are adjusted when a child can’t recognize symptoms of low blood sugar, doesn’t have access to monitoring technology, or when tighter control would take a toll on their well-being or mental health.
HbA1c During Pregnancy
Pregnancy changes what counts as normal. Red blood cells turn over faster during pregnancy, which naturally lowers HbA1c readings. Research on pregnant women without diabetes found that typical values run below 5.4% in the first and second trimesters, rising slightly to below 5.7% in the third trimester. For women with type 1 diabetes planning pregnancy, the ADA recommends getting HbA1c between 6% and 6.5% before conception, with the goal of going even lower during pregnancy itself.
Conditions That Skew Results
Several common health conditions can make your HbA1c reading inaccurately high or low, and some of these become more prevalent with age.
Iron-deficiency anemia pushes HbA1c readings falsely high. The mechanism involves a compound that increases during iron deficiency and enhances sugar attachment to red blood cells. If you’re anemic, your HbA1c might overstate your actual average blood sugar until the anemia is treated.
Conditions that shorten red blood cell lifespan, such as blood loss or certain types of anemia where red blood cells break down prematurely, will produce falsely low readings. The cells simply don’t live long enough to accumulate sugar at the expected rate. Kidney disease, which is more common in older adults, also interferes with accuracy. For people on dialysis, HbA1c tends to underestimate blood sugar, and alternative markers may give a more reliable picture.
Certain genetic hemoglobin variants, more common in people of African, Mediterranean, or Southeast Asian descent, can also affect results depending on the lab method used. If your HbA1c doesn’t match your daily glucose readings, one of these factors may be at play.
How Lifestyle Changes Affect HbA1c by Age
Diet and exercise interventions can meaningfully lower HbA1c, but the size of the improvement varies by age. A 2025 study of a community-based lifestyle program found the largest reductions in people aged 40 to 49, whose HbA1c dropped by 0.83% to 1.18%. People aged 50 to 65 still saw significant improvements but with a smaller range of 0.61% to 1.16%. Beyond age 65, improvements plateaued and were no longer statistically significant in that particular study.
This doesn’t mean lifestyle changes are pointless for older adults. It does suggest that the metabolic response to the same interventions becomes more variable, and that people over 65 may need more sustained or targeted approaches to see measurable shifts in their HbA1c.