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Hemoglobin A1c (HbA1c) calculated from capillary blood

Published: August 9, 2026Updated: August 16, 2026

This test measures the average blood sugar level over the past 2–3 months by analyzing hemoglobin that has been linked to glucose. It helps doctors assess long-term blood sugar control.

Quick summary

["HbA1c reflects your blood sugar trends over time, aiding diabetes management."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
20509-6
Short code
Hgb Bld Calc-mCnc
Synonyms
Hgb Bld Calc-mCnc
Category
hematology
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
12
Ref high
17.5
Critical range
7 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
calculated
CPT
85018
SNOMED
900000000000003004
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

How This Test Works

Your blood sample is collected from a fingerstick (capillary blood) and processed to determine the percentage of hemoglobin molecules bound to glucose. This value is then calculated to provide an HbA1c result, which accounts for variations in red blood cell lifespan and hemoglobin types.

Why It Matters for You

HbA1c is a key indicator of how well your diabetes or prediabetes is managed. It provides a snapshot of your average blood sugar levels over time, helping your healthcare team adjust treatments like diet, exercise, or medication.

Common Uses

This test is typically used to diagnose diabetes, monitor long-term blood sugar control, and assess the effectiveness of treatment plans in people with diabetes or prediabetes.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small amount of blood drawn from your finger, similar to a standard blood sugar check. If you’re on insulin or certain medications, let your provider know before the test.

Reference range

Adult males: 13.5-17.5 g/dL; Females: 12.0-16.0 g/dLN/A

Specimen: whole-blood

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

HbA1c (calculated)

Frequently asked questions

What does an abnormal HbA1c result mean?
An HbA1c result above the typical range for your condition may indicate poor blood sugar control, which could increase your risk of diabetes complications like nerve damage, kidney disease, or heart problems. A result below the range may suggest your blood sugar is consistently low, which can also have risks. Your doctor will discuss your specific result and next steps.
How often should I get this test?
The frequency depends on your health status. People with diabetes usually get this test every 3–6 months, while those at high risk for prediabetes may need it more often. Your healthcare provider will determine the best schedule for you.
Can lifestyle changes affect my HbA1c result?
Yes! Making healthy choices like eating balanced meals, staying active, and managing stress can improve your HbA1c levels. Consistently following these habits may lead to better long-term blood sugar control and a more accurate HbA1c result.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy