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Hemoglobin
A1C
(HbA1c) Test

Overview
The A1C test is a common blood test for diagnosing diabetes.
For people living with diabetes, the test checks how well
they manage blood sugar levels. The A1C test also is called
the glycated hemoglobin, glycosylated hemoglobin, hemoglobin
A1C or HbA1c test. An A1C test result shows the average blood sugar level over
the past 2 to 3 months. The A1C test measures what
percentage of hemoglobin in the blood is coated with sugar,
also called glycated. The higher the A1C level is, the poorer the blood sugar
management. And the higher the risk of having health
concerns related to diabetes.
What is the A1C test?
The A1C test is a blood test that provides information about
your average levels of blood glucose, also called blood
sugar, over the past 3 months. The A1C test is also the primary test
used for diabetes management.
An A1C test may be used to screen for or diagnose:
-
Type 2 diabetes. With type 2 diabetes your
blood glucose gets too high because your body doesn't
make enough insulin to move blood sugar from your
bloodstream into your cells, or because your cells stop
responding to insulin.
-
Prediabetes. Prediabetes means that your
blood glucose levels are higher than normal, but not
high enough to diagnosed as diabetes. Lifestyle changes,
such as healthy
eating and exercise,
may help delay or prevent prediabetes from becoming type
2 diabetes.
The A1C test is sometimes called the hemoglobin A1C, HbA1c, glycated
hemoglobin, or glycohemoglobin test. Hemoglobin is the part of a red
blood cell that carries oxygen to the cells. Glucose attaches to or
binds with hemoglobin in your blood cells, and the A1C test is based on
this attachment of glucose to hemoglobin.
The higher the glucose level in your bloodstream, the more glucose will
attach to the hemoglobin. The A1C test measures the amount of hemoglobin
with attached glucose and reflects your average blood glucose levels
over the past 3 months.
The A1C test result is reported as a percentage. The higher the
percentage, the higher your blood glucose levels have been. A normal A1C
level is below 5.7 percent.
Why is Hemoglobin A1c important?
What is an A1C test?
An A1C test measures the average amount of glucose (sugar) in your
blood over the past three months. The result is reported as a
percentage. The higher the percentage, the higher your blood glucose
levels have been, on average.
A1C is a simple blood test that healthcare providers use to:
- Diagnose prediabetes. If you have prediabetes, you have
a higher risk of getting diabetes and cardiovascular
disease.
- Diagnose diabetes. To confirm a diabetes diagnosis, your
healthcare professional may look at the results of two
blood tests. These can be either two A1C tests or the
A1C test plus another test, such as a fasting blood
sugar test, also called blood glucose test.
- Check your diabetes treatment plan. The result of a
first A1C test also gives you a starting A1C level. It's
compared to future A1C test results to see how well your
diabetes treatment plan is working.
Healthcare providers do A1C tests in one of two ways:
- A phlebotomist takes
a blood sample from your vein and sends it to a lab for analysis
(the most common form of the test).
- A provider gets a sample of your blood from a finger prick. They
usually get the results from this test within minutes. This form
of the test is only for assessing your management, not for
diagnosis.
The vein blood test is generally more accurate than the finger prick
blood test.
Other names for an A1C test include:
- Hemoglobin A1C.
- HbA1c.
- Glycated hemoglobin.
- Glycohemoglobin test.
What is blood glucose (sugar)?
Glucose (sugar) mainly comes from carbohydrates in
the food and drinks you consume. It’s your body’s main source of
energy. Your blood carries glucose to all of your body’s cells to
use for energy.
Several bodily processes help keep your blood glucose in a healthy
range. Insulin,
a hormone your pancreas makes,
is the most significant contributor to maintaining healthy blood
sugar.
If you have consistently elevated blood glucose levels (hyperglycemia)
— and an elevated A1C result — it usually indicates diabetes.
Diabetes develops when your pancreas doesn’t make any insulin or
enough insulin, or your body isn’t using insulin properly.
When would I need an A1C test?
If you have diabetes, you should have an A1C test two or more times
a year to see how well your management plan is working. Your
healthcare team will recommend exactly how often you should get this
test.
If you don’t have a diabetes diagnosis, a healthcare provider may
order an A1C test if you have symptoms of the condition, including:
- Intense thirst (polydipsia).
- Increased urination (peeing).
- Blurry vision.
- Fatigue, or feeling tired all the time.
You may also get an A1C test to screen for Type 2 diabetes if you’re
at risk for the condition.
Risk factors include:
How often do I need an A1C test?
How often you need an A1C test depends on the type of
diabetes, your treatment plan, your treatment goals and what
your healthcare professional decides. For example, you may
have an A1C test:
- Once every year if you have prediabetes.
- Twice a year if you don't use insulin and your blood
sugar level stays within your target range.
You may need A1C tests more often if you use insulin or if
have trouble keeping your blood sugar level within your
target range. You also may have A1C tests if your healthcare
professional changes your diabetes treatment plan or you
begin taking a new diabetes medicine.
Test Details
How is A1C calculated?
A1C testing relies on hemoglobin. Hemoglobin is the part of
the red
blood cell that carries oxygen throughout your body.
When you have glucose in your blood, it sticks to
hemoglobin. This is called glycation. The more glucose is in
your blood, the more it sticks. And it can stay there for
around three months — about how long the average red blood
cell lives.
The A1C test measures the average amount of glucose that’s
been attached to hemoglobin over time. Because the A1C test
measures glucose levels over a period of time, it provides
more information about blood sugar than a single blood sugar
test.
Do I need to fast for an A1C test?
No, the test doesn't require fasting beforehand, so you’re
free to eat and drink normally. But if you have other blood
tests scheduled at the same time, they may require special
prep. Check with your doctor.
What should I expect during an A1C test?
During the A1C test, a member of your healthcare team takes
a blood sample by putting a needle into a vein in your arm
or pricking your finger with a small, pointed tool.
Blood taken from a vein goes to a lab for testing. Your
healthcare team may look at blood from a finger prick for
results right away. You have this in-office test only to
check on your treatment plan. You won't have it for
diagnosis or screening.
You can expect the following during an A1C test that
involves a sample from your vein, or a blood draw:
- You’ll sit in a chair, and a phlebotomist will check
your arms for an easily accessible vein. This is usually
in the inner part of your arm on the other side of your
elbow.
- Once they’ve located a vein, they’ll clean and disinfect
the area.
- They’ll then insert a small needle into your vein to
take a blood sample. This may feel like a small pinch.
- After they insert the needle, a small amount of blood
will collect in a test tube.
- Once they have enough blood to test, they’ll remove the
needle and hold a cotton ball or gauze on the site to
stop the bleeding.
- Finally, they’ll place a bandage over the site, and
you’ll be finished.
You can expect the following during a finger prick A1C test:
- A healthcare provider will ask you which finger you’d
like them to use.
- They’ll disinfect your fingertip with an alcohol swab
and prick it with a small needle called a lancet, which
is usually contained within a small plastic device.
- They’ll squeeze your fingertip to form a drop of blood
and collect the drop in a small plastic container.
- After they have enough blood for the test, they’ll give
you a cotton ball or gauze to hold against your
fingertip to stop the bleeding.
- The results are usually ready within minutes.
What are the risks of an A1C test?
Blood tests are a very common and essential part of medical
testing and screening. There’s very little risk to having
either type of A1C test. You may have slight tenderness or
a bruise at
the site of the blood draw or finger prick, but this usually
resolves quickly.
Results and Follow-Up
What does my A1C mean?
An A1C test result is reported as a percentage. The number
represents the portion of hemoglobin proteins that are
glycated, or holding glucose. The higher the percentage, the
higher your blood sugar levels have been over the last few
months.
For diagnosing purposes, an A1C level of:

If you already have diabetes, an A1C result is a glimpse
into how well your management plan has been working over the
last three months. Management may involve oral pills, taking
insulin, monitoring blood sugar levels and/or lifestyle
changes, such as diet and exercise. Your A1C can help you
and your provider determine if you should adjust any part of
your treatment plan.
It’s important to remember that your A1C (if you have
diabetes) is just an average measurement of your blood sugar
over a few months. It’s not a grade or the ultimate
determiner of whether you’re living a healthy life. Know
that your A1C will change over your lifetime and that there
are steps you can take to improve your diabetes management
and A1C level, if needed.
A1C and estimated average glucose (eAG)
Another term you may come across when finding out your A1C
is eAG. Your doctor might report your A1C results as eAG.
eAG is similar to what you see when monitoring your blood
glucose at home on your meter. However, because you are more
likely to check your blood glucose in the morning and before
meals, your meter readings will likely be lower than your
eAG.
Some laboratories report your A1C results as a percentage in
addition to the corresponding estimated average glucose
(eAG).
The eAG calculation converts the A1C percentage to the same
units you use with at-home glucose meters (glucometers) —
milligrams per deciliter (mg/dL) or millimoles per liter
(mmol/L). Just like your A1C is an average, the eAG is a
single number that represents your average blood sugar level
over the past three months.
For example, an A1C level of 7% equates to an eAG of 154
mg/dL (8.6 mmol/L). An A1C level of 9% equates to an eAG of
212 mg/dL (11.8 mmol/L).
Comparison of A1C and eAG
meter readings
|
A1C |
eAG |
|
% |
mg/dL |
mmol/L |
In Range |
< 5.7 |
< 117 |
< 6.5 |
Prediabetes |
6 |
126 |
7.0 |
Diabetes |
6.5 |
140 |
7.8 |
7 |
154 |
8.6 |
7.5 |
169 |
9.4 |
8 |
183 |
10.0 |
8.5 |
197 |
11.0 |
9 |
212 |
11.8 |
9.5 |
226 |
12.6 |
10 |
240 |
13.4 |
11 |
269 |
14.9 |
12 |
298 |
16.5 |
13 |
326 |
18.1 |
14 |
355 |
19.7 |
What is a normal A1C?
For people without diabetes, a normal A1C is below 5.7%.
For people with diabetes, what’s “normal” and healthy for
you depends on your goals and access to diabetes management
medication and tools. Together, you and your healthcare
provider will determine an A1C range that should be your
target goal. This will likely change throughout your life.
In general, the American Diabetes Association recommends
that the goal for most adults with diabetes should be an A1C
of 7% or lower.
Your A1C goals may be above 7% if you have:
- Limited life expectancy.
- Severe low blood sugar (hypoglycemia)
episodes or are unable to sense these episodes
(hypoglycemia unawareness).
- Advanced diabetes complications, such as chronic kidney
disease, nerve problems or cardiovascular disease.
On the other hand, healthcare providers typically recommend
that people with Type 1 diabetes who are pregnant try to
maintain an A1C of 6.5% or lower throughout their pregnancy.
This is to try to lower potential health risks for the fetus
and to try to prevent fetal
macrosomia.
Blood Glucose Measurements Compared with A1C
Measurements over 4 Days

Blood glucose (mg/dL) measurements were taken four times per
day (fasting or pre-breakfast, pre-lunch, pre-dinner, and
bedtime).
The straight black line shows an A1C measurement of 7.0
percent. The blue line shows an example of how blood glucose
test results might look from self-monitoring four times a
day over a 4-day period.
A1C levels by age
Age is one of many factors that affect a person’s blood
glucose levels. However, while advancing age is associated
with increased blood glucose levels, the changes are often
small. Research from 2019 defined age-related A1C percentage levels in
healthy populations as:
Age group |
All respondents |
Men |
Women |
20 to 39
years |
4.0 to 6.0 |
4.1 to 6.1 |
4.0 to 5.8 |
40 to 59
years |
4.1 to 6.2 |
4.0 to 6.2 |
4.1 to 6.1 |
≥ 60 years |
4.4 to 6.6 |
4.4 to 6.6 |
4.4 to 6.5 |
What is a dangerous level of A1C?
The higher your A1C levels, especially if they’re
consistently high over several years, the more likely you’ll
develop complications, such as:
- Retinopathy, Vision loss or blindness
- Nephropathy, Kidney failure
- Neuropathy, or nerve damage, which most commonly affects
your hands, feet, arms, and legs
- Gastroparesis,
or paralysis of the stomach, in which your stomach
cannot properly digest food
-
Heart disease.
- Stroke.
Studies have shown that people with diabetes may be able to
reduce the risk of diabetes complications by consistently
keeping their A1C levels below 7%.
It’s important to remember that other factors can contribute
to the development of diabetes complications, such as
genetics and how long you’ve had diabetes.
Are A1C tests accurate?
When repeated, the A1C test result can be slightly higher or
lower than the first measurement. This means, for example,
an A1C reported as 6.8 percent on one test could be reported
in a range from 6.4 to 7.2 percent on a repeat test from the
same blood sample 7.3 In the past, this range was larger but
new, stricter quality-control standards mean more precise
A1C test results.
Certain factors can affect the accuracy of A1C tests,
including:
- Genetics, such as hemoglobin variants.
- Medical conditions.
- Medications and supplements.
- Errors in the collection, transport or processing of the
test.
These factors can make your result falsely low or falsely
high. Most of the factors are due to differences in the
lifespan and health of your red blood cells.
Hemoglobin variants and A1C results
Hemoglobin variants can affect the results of some A1C
tests.
The form of hemoglobin in your blood depends on the genes
you inherit from your biological parents. There are many
different forms. The most common form is hemoglobin A.
Other, less common forms of hemoglobin are called hemoglobin
variants.
A hemoglobin variant doesn’t increase your risk of
developing diabetes, but it can affect A1C results. Labs
have different ways to do A1C tests on blood with a
hemoglobin variant.
The most common variants include:
-
Hemoglobin C trait: Black people, people of
West African descent and people from South and Central
America, the Caribbean Islands and Europe are most
likely to have this trait.
-
Hemoglobin D trait: People who live in China,
India, Turkey, Brazil and some parts of Europe are most
likely to have this trait.
-
Hemoglobin E trait: Asian Americans, especially
those of Southeast Asian descent, are most likely to
have this trait.
-
Hemoglobin S trait: Black people and Hispanic
Americans are most likely to have this trait.
A blood test can detect hemoglobin variants. Talk to your
healthcare provider if you think you might have a hemoglobin
variant that could affect your A1C results.
Causes of falsely low A1C results
The following conditions and situations can cause falsely
low A1C results, meaning the result is lower than your
actual A1C level:
- Alcohol use disorder.
- Blood transfusion.
- Chronic kidney
failure.
- Erythropoietin-stimulating agents (ESAs).
- Hemorrhage (bleeding).
- Living at a high altitude.
- Iron supplementation.
- Cirrhosis of the liver.
- Pregnancy.
- Sickle cell anemia.
- Spherocytosis and hemolytic
anemia.
Causes of falsely high A1C results
The following conditions and situations can cause falsely
high A1C results, meaning the result is higher than your
actual A1C level:
- Anemia, such as iron-deficiency
anemia, infection-induced anemia or tumor-induced
anemia.
- Certain medications, including immunosuppressant medications
and protease inhibitors.
- Hypertriglyceridemia.
High triglycerides, a type of fat that circulates in
your bloodstream
- Organ transplantation.
- Thalassemia,
, a blood disorder that keeps your body from producing a
normal amount of hemoglobin and red blood cells.
-
Vitamin B12 deficiency.
Can you have a high A1C and not have diabetes?
If you have an elevated A1C (above 6.5%) for the first time,
it doesn’t always mean that you have diabetes. Other
factors, such as certain medications (like steroids) or
sickness can temporarily increase your blood sugar levels.
Anemia and other conditions can cause a falsely high A1C
result, as well. There also could’ve been an error in the
collection, transport or processing of the test.
Healthcare providers rely on more than one test to diagnose
diabetes. For example, they may order a fasting
blood glucose test or another A1C test. In any case,
your provider will carefully interpret your results and
discuss them with you.
Limitations of the A1C test
The A1c test is a valuable tool for diagnosing and managing
diabetes, but it’s not perfect. As detailed above, it’s not
always accurate. Another limitation is that it does not tell
you how your blood sugar level fluctuates throughout the
day, week, or month. Such fluctuations are particularly
common in type 1 diabetes. Because the test only gives an
average blood sugar level over the previous 3 months, your
result could be the same whether your blood sugar fluctuates
a lot or stays steady.
Why is that important? Your goal is to keep your blood sugar
level in your desired range as much as possible. Your "time
in range" numbers provide a better picture of how well you
manage your diabetes day to day and week to week. The A1c
was not designed to do that. For that, you need a continuous
glucose monitor, which tracks your glucose level 24/7.
Some factors may make A1C test results less exact.
These include:
- Pregnancy.
- Recent or heavy blood loss.
- Recently receiving blood from a donor, called a transfusion.
- Sometimes, a condition that results in not having enough red blood
cells, called anemia.
- Certain blood conditions, such as sickle cell anemia.
- Other forms of hemoglobin in the body.
Hemoglobin is a protein that carries oxygen through the blood. The most
common form of hemoglobin protein is called hemoglobin A. If there are
other forms of hemoglobin in the blood, called variants, the A1C test
results may not be right. Hemoglobin variants are more common among
people of African, Mediterranean or Southeast Asian descent.
If you have a hemoglobin variant, your test may need to go to a special
lab. Or you may need another test to diagnose diabetes and check on its
treatment.
What A1C goal should I have?
People will have different A1C targets, depending on their diabetes
history and their general health. You should discuss your A1C target
with your health care professional. Studies have shown that some people
with diabetes can reduce the risk of diabetes
complications by keeping A1C levels below 7 percent.
Managing blood glucose early in the course of diabetes may provide
benefits for many years to come. However, an A1C level that is safe for
one person may not be safe for another. For example, keeping an A1C
level below 7 percent may not be safe if it leads to problems with hypoglycemia,
also called low blood glucose.
Less strict blood glucose control, or an A1C between 7 and 8 percent—or
even higher in some circumstances—may be appropriate in people who have
- limited life expectancy
- long-standing diabetes and trouble reaching a lower goal
- severe
hypoglycemia or inability to sense hypoglycemia (also called
hypoglycemia unawareness)
- advanced diabetes complications such as chronic
kidney disease, nerve problems, or
cardiovascular disease
This chart details goals for specific groups of people with
diabetes, based on age:
Age |
Before meals (fasting) |
After eating |
Children and teens
|
90 to 130 mg/dL |
|
Adults |
80 to 130 mg/dL |
< 180 mg/dL
(1 or 2 hours after) |
Pregnant |
70 to 95 mg/dL |
110 to 140 mg/dL
(1 hour after);
100 to 120 mg/dL
(2 hours after) |
65 and older |
80 to 130 mg/dL |
|
Without diabetes |
99 mg/dL or below |
140 mg/dL |
It’s important to remember that age alone isn’t a deciding
factor on your blood sugar targets.
When to contact a doctor
A person should make an appointment with their doctor if they:
- have questions or concerns about their treatment plan
- are finding it hard to keep their blood glucose levels within
the target range
- have had symptoms of high or low blood glucose levels
- think they might have complications of diabetes
Symptoms of high blood glucose levels include:
- fatigue
- unusual thirst
- frequent urination
- blurred vision
Symptoms of low blood glucose levels include:
- nervousness, irritability, or anxiety
- confusion
- dizziness
- hunger
- shaking
- sweating
Anyone who develops any of the symptoms above or notices other
changes in their health should inform a doctor.
Additional Details
Is A1C an accurate representation of diabetes management?
For decades, healthcare providers and people with diabetes
have relied on A1C as the main way to gauge how well their
management of the condition is working.
For people with
Type 1 diabetes, in particular, blood sugar
can fluctuate significantly throughout the days, weeks and
months. Because of this, A1C isn’t always an accurate
measurement of management since it’s based on an average.
For example, a person who has frequent blood sugar
fluctuations between significantly low and high episodes may
have an A1C of 7%. A person who has blood sugar levels that
stay more consistently around 154 mg/dL may also have an A1C
of 7%.
More recently, with the invention of continuous
glucose monitoring (CGM) devices, providers and people
with diabetes have found time
in range (TIR) to be a more helpful and accurate
representation of diabetes management.
Time in range is the amount of time your blood sugar levels
are in a recommended target range. TIR is measured as a
percentage. Blood sugar range goals can vary for each
person, but a typical target range is between 70 and 180 mg/dL.
For most adults with Type 1
diabetes or
Type 2 diabetes, providers
recommend aiming to have a TIR above 70% (about 17 hours of
a 24-hour day).
With CGMs and TIR, providers and people with diabetes can
see how often they’re experiencing high or low blood sugar
episodes. This can help them more accurately adjust
treatment strategies.
FAQ's
What does a
hemoglobin A1c test measure?
This test measures your average blood sugar (aka blood glucose) level
over the previous 3 months. It is used to diagnose and manage diabetes.
What is a
normal A1c range by age?
A1c tests calculate the percentage of blood sugar in your bloodstream.
The normal range, meaning you don’t have diabetes, is below 5.7%. That
normal range remains the same no matter your age.
Does a high
A1c level mean I have diabetes?
Maybe. If you have no symptoms of diabetes when you take the test, your
doctor will schedule a follow-up A1c test to confirm the result. Also,
several health conditions and other factors can make the A1c test less
accurate, potentially causing falsely high or falsely low results. Your
doctor should consider these factors when evaluating your A1c test
result.
What happens
if your hemoglobin is low?
Low levels of hemoglobin keep your body from delivering enough oxygen to
tissues. As a result, you feel tired and weak, and your body can’t
function like it should.
What happens
if your hemoglobin is high?
High levels of hemoglobin thicken your blood. This keeps it from flowing
as easily, which means your organs can’t get the amount of oxygen they
need. You may get headaches, dizziness, blurred or double vision,
itching, and blood clots.
Is high or low
hemoglobin bad?
Your hemoglobin levels give
your doctor important information about the health of your red blood
cells. Both high and low levels of hemoglobin can be signs that your
tissues and organs aren’t getting the oxygen they need. They can also
indicate underlying problems.
Is high
hemoglobin something to worry about?
Some causes of high hemoglobin can be serious, such as bone marrow
disease, congenital heart disease, heart failure, and scarred lungs. But
other factors that can cause it include time spent at a high altitude
and dehydration. Your doctor can test you for conditions that may be
raising your hemoglobin levels.
What causes
hemoglobin to be a little high?
Most often, high hemoglobin happens because your blood oxygen levels
have been low for some time. This might be because of an illness or
injury. Your doctor will examine you and may do tests to find out what’s
behind your high hemoglobin levels.
One Final Note..
A doctor orders an A1C test to check whether someone has
prediabetes or type 1 or 2 diabetes. Doctors also use this
test to monitor blood glucose levels in people with diabetes
to check how well their treatment plan is working.
A1C test results are usually a percentage but may come as an
eAG measurement. Target A1C levels vary from person to
person, depending on age, overall health, and other factors.
Having high A1C levels may indicate a person has diabetes or
a high risk of related complications. In this case, a doctor
will work with the individual to adjust the treatment
approach.
It can be stressful to see an abnormal or
higher-than-you-expected A1C result. Know that having an
elevated A1C for the first time doesn’t necessarily mean you
have diabetes. Several factors can cause inaccurate results.
Your healthcare provider will let you know if you need to
undergo further tests. Don’t be afraid to ask your provider
questions. They’re available to help you.
If you have diabetes, it’s important to remember that your
A1C is just a temporary average of your blood sugar levels.
Know that there are steps you can take to change your A1C
level. If you’re feeling overwhelmed with diabetes
management, talk to your healthcare provider. Together, you
can formulate a plan to get closer to your management and
A1C goals.
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