Your doctor just told you your A1C is 6.8%. What does that actually mean? Is it good? Bad? Dangerous?
The hemoglobin A1C test is one of the most important tools in diabetes management and diagnosis, but the results can be confusing. Let's break down exactly what A1C measures and what your numbers mean.
What Is Hemoglobin A1C?
The Science Behind A1C
Hemoglobin A1C (often just called A1C) measures the percentage of hemoglobin in your red blood cells that has glucose attached to it.
How it works:
- Glucose in your bloodstream sticks to hemoglobin (a protein in red blood cells)
- Once attached, it stays there for the life of the red blood cell (~3 months)
- The test measures what percentage of hemoglobin is "sugar-coated"
Think of it this way: If your blood sugar is high, more sugar coats your hemoglobin. If it's normal, less coating occurs.
Why A1C Is Useful
| Advantage | Explanation |
|---|---|
| No fasting required | Can be done anytime of day |
| Long-term picture | Reflects average over 3 months |
| Standardized | Results consistent across labs worldwide |
| Predictive | Correlates with complication risk |
A1C Ranges: What's Normal, Prediabetes, and Diabetes?
The 2025 ADA guidelines establish these categories:
| Category | A1C Range | Estimated Average Glucose |
|---|---|---|
| Normal | Below 5.7% | Below 117 mg/dL |
| Prediabetes | 5.7% - 6.4% | 117 - 137 mg/dL |
| Diabetes | 6.5% or higher | 140 mg/dL or higher |
The A1C to Average Glucose Conversion
Researchers have established how A1C relates to estimated average glucose (eAG):
| A1C | Estimated Average Glucose | A1C | Estimated Average Glucose |
|---|---|---|---|
| 4% | 68 mg/dL | 8% | 183 mg/dL |
| 5% | 97 mg/dL | 9% | 212 mg/dL |
| 6% | 126 mg/dL | 10% | 240 mg/dL |
| 7% | 154 mg/dL | 11% | 269 mg/dL |
| 7.5% | 169 mg/dL | 12% | 298 mg/dL |
Calculation: eAG (mg/dL) = 28.7 × A1C - 46.7
Interpreting Your A1C Result
A1C Below 5.7%: Normal
Your blood sugar levels are in the healthy range.
- Risk: Low
- Action: Continue healthy habits; retest every 3 years if at risk
A1C 5.7% - 6.4%: Prediabetes
Your blood sugar is higher than normal but not yet in the diabetes range.
- Risk: High—5-10% progress to diabetes annually without intervention
- Action:
- Lifestyle changes (weight loss 5-7%, regular exercise)
- Consider diabetes prevention program
- Annual retesting
A1C 6.5% or Higher: Diabetes
Your A1C is in the diabetes range.
- Risk: Very high—complications can develop over time
- Action:
- Confirm with repeat test if no symptoms
- Start comprehensive diabetes management
- Regular monitoring (every 3 months if not at target)
A1C Targets for People with Diabetes
General Target: Below 7.0%
For most non-pregnant adults with diabetes, the target A1C is <7.0%.
This target balances:
- Benefit: Significant reduction in microvascular complications (eye, kidney, nerve damage)
- Risk: Low risk of hypoglycemia (dangerously low blood sugar)
Personalized A1C Targets
The 2025 guidelines emphasize individualized targets based on patient factors:
| Patient Profile | A1C Target | Rationale |
|---|---|---|
| Young, healthy, short duration | < 6.5% | Prevent long-term complications |
| Most adults | < 7.0% | Standard balance of benefit/risk |
| History of severe hypoglycemia | < 8.0% | Safety first—avoid dangerous lows |
| Limited life expectancy | < 8.0-8.5% | Minimize treatment burden |
| Older adults (≥65) | 7.5-8.0% | Prevent falls, confusion |
| Pregnancy planning | < 6.0% | Reduce birth defect risk |
| Pregnancy (with diabetes) | < 6.0-6.5% | Optimal fetal outcomes |
When Tighter Control (Lower A1C) May Be Appropriate
Consider A1C < 6.5% for:
- Patients with short duration of diabetes
- Patients without significant hypoglycemia
- Patients without cardiovascular disease
- Younger patients with long life expectancy
- Patients highly motivated to manage diabetes
When Less Stringent Control (Higher A1C) May Be Appropriate
Consider A1C 7.5-8.0% or higher for:
- Patients with history of severe hypoglycemia
- Patients with limited life expectancy
- Patients with advanced complications
- Older adults at risk for falls
- Patients with difficulty adhering to treatment
Factors That Can Affect A1C Accuracy
Conditions That Falsely Elevate A1C
| Condition | Why It Happens |
|---|---|
| Iron deficiency anemia | Decreased red cell turnover, older cells |
| Vitamin B12 deficiency | Decreased red cell turnover |
| Kidney failure | Carbamylation of hemoglobin |
| High altitude | Increased red cell turnover |
| Recent transfusion | Donor blood affects result |
Conditions That Falsely Lower A1C
| Condition | Why It Happens |
|---|---|
| Hemolytic anemia | Shortened red cell lifespan |
| Sickle cell trait/disease | Variant hemoglobin |
| Pregnancy | Increased red cell turnover |
| Recent blood loss | Younger red blood cells |
| Liver disease | Decreased hemoglobin production |
| Recent blood transfusion | Normal donor blood dilutes result |
Hemoglobin Variants
If you have a hemoglobin variant (like sickle cell trait or thalassemia):
- Some A1C assays may be inaccurate
- Point-of-care tests may give unreliable results
- Alternative testing: Consider fructosamine, estimated average glucose from CGM, or frequent fasting glucose checks
A1C vs. Daily Blood Sugar Monitoring
The Pros and Cons
| Method | What It Measures | Advantages | Limitations |
|---|---|---|---|
| A1C | 3-month average | No fasting, reflects trends | Doesn't show daily patterns |
| Fingerstick glucose | Point-in-time | Immediate results | Doesn't show overall picture |
| CGM (Time in Range) | Daily patterns | Shows highs, lows, variability | Requires device |
Why Both Matter
- A1C tells you and your doctor about overall control and complication risk
- Daily monitoring helps you understand how food, activity, and medications affect your blood sugar day-to-day
- CGM data provides even more detail, including time in range, variability, and nocturnal patterns
Key insight: You can have a "good" A1C but still have problematic daily patterns (lots of highs and lows that cancel out). That's why CGM is increasingly recommended.
How Often to Check A1C
For People WITHOUT Diabetes
- Every 3 years starting at age 35
- More frequently if you have risk factors (overweight, family history, etc.)
For People WITH Prediabetes
- Annually to monitor for progression
For People WITH Diabetes
| Situation | Testing Frequency |
|---|---|
| Not at goal | Every 3 months |
| At goal and stable | Every 6 months |
| Changing therapy | Every 3 months |
What Affects Your A1C Result?
Factors Within Your Control
| Factor | Impact | Magnitude |
|---|---|---|
| Carbohydrate intake | Significant | High intake raises A1C |
| Physical activity | Moderate | Regular activity lowers A1C |
| Weight | Significant | Weight loss of 5-10% can reduce A1C by 0.5-1.0% |
| Stress | Moderate | Chronic stress can raise A1C |
| Sleep | Moderate | Poor sleep affects insulin sensitivity |
| Medication adherence | Significant | Missing doses raises A1C |
Factors Outside Your Control
- Genetics: Some people are predisposed to higher A1C
- Duration of diabetes: A1C tends to rise over time without treatment intensification
- Illness: Acute illness can temporarily affect readings
- Medications: Some (like steroids) can significantly raise blood sugar
Lowering Your A1C: What Works?
Evidence-Based Strategies
| Intervention | Typical A1C Reduction |
|---|---|
| Metformin | 1.0-1.5% |
| Sulfonylureas | 1.0-1.5% |
| GLP-1 agonists | 0.5-1.5% |
| SGLT2 inhibitors | 0.5-1.0% |
| DPP-4 inhibitors | 0.5-0.8% |
| Insulin | 1.5-3.5% (dose-dependent) |
| Weight loss (5-10%) | 0.5-2.0% |
| Structured exercise | 0.5-1.0% |
| Carbohydrate restriction | 0.5-1.5% |
Combination Effects
Combining interventions often produces additive effects:
- Weight loss + metformin: ~2% reduction common
- Metformin + GLP-1: ~2% reduction possible
- Triple therapy can achieve 3%+ reduction
Key Takeaways
- A1C below 5.7% is normal—6.5% or higher indicates diabetes
- General target is < 7.0% for most adults with diabetes
- Targets are individualized—your goal may differ based on your situation
- A1C can be inaccurate in certain medical conditions
- A1C and daily monitoring complement each other—both are important
- Lifestyle changes can lower A1C 0.5-1.0%; medications add additional reduction
FAQ Section
What is a normal A1C level?
A normal A1C is below 5.7%. For someone without diabetes, A1C typically ranges from 4% to 5.6%. Prediabetes is 5.7-6.4%, and diabetes is 6.5% or higher.
How can I lower my A1C quickly?
The fastest ways to lower A1C are:
- Starting insulin or combination therapy (if prescribed)
- Carbohydrate restriction (reducing sugar, bread, pasta, rice)
- Daily physical activity (walking after meals)
- Weight loss (even 5% makes a difference)
A1C reflects a 3-month average, so significant changes typically take 2-3 months to fully show in your result.
Why is my A1C high when my daily glucose is normal?
This discrepancy can occur if:
- You have undetected nighttime highs
- You have post-meal spikes you're not catching
- Your A1C test was affected by a medical condition (anemia, kidney disease)
- Your glucose meter or fingerstick technique is inaccurate
Consider asking your doctor about CGM to see your full glucose picture.
Can A1C be wrong?
Yes. A1C can be inaccurate if you have:
- Anemia (iron or B12 deficiency)
- Hemoglobin variants (sickle cell, thalassemia)
- Recent blood transfusion
- Kidney or liver disease
- Pregnancy
If you have these conditions, your doctor may use fasting glucose, OGTT, or fructosamine instead.
What A1C level requires insulin?
There's no specific A1C threshold that automatically requires insulin. However, insulin is typically considered when:
- A1C remains above target despite two or three oral medications
- A1C is very high at diagnosis (≥ 10%)
- You have symptoms of severe hyperglycemia
- You're losing weight unintentionally
- You're pregnant or planning pregnancy
Sources:
- American Diabetes Association. Standards of Care in Diabetes—2025. Diabetes Care 2025; 48(Suppl 1)
- Nathan DM, et al. Diabetes Care 2008; 31:1473-1478 (eAG study)
- ADA A1C Information