1. HbA1c
Definition
HbA1c is a test that measures the amount of glycated hemoglobin in your blood.
Glycated hemoglobin is a substance in red blood cells that is formed when blood sugar
(glucose) attaches to hemoglobin.
Alternative Names
Glycated hemoglobin; Glycosylated hemoglobin; Hemoglobin - glycosylated; A1C;
GHb; Glycohemoglobin; Diabetic control index
How the Test is Performed
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand.
The puncture site is cleaned with germ-killing medicine (antiseptic). The health care
provider wraps an elastic band around the upper arm to apply pressure to the area and
make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects
into an airtight vial or tube attached to the needle. The elastic band is removed from your
arm. Once the blood has been collected, the needle is removed, and the puncture site is
covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin
and make it bleed. The blood collects into a small glass tube called a pipette, or onto a
slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to Prepare for the Test
No special preparation is necessary.
How the Test Will Feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or
stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Your doctor may order this test if you have diabetes. It is used to measure your blood
sugar control over several months. It can give a good estimate of how well you have
managed your diabetes over the last 2 or 3 months.

2. You have more glycated hemoglobin if you have had high levels of glucose in your
blood. In general, the higher your HbA1c, the higher the risk that you will develop
problems such as:
• Eye disease
• Heart disease
• Kidney disease
• Nerve damage
• Stroke
This is especially true if your HbA1c remains high for a long period of time.
The closer your HbA1c is to normal, the less risk you have for these complications.
Normal Results
An HbA1c of 6% or less is normal. If you have diabetes, you should try to keep your
HbA1c level at or below 7%. However, you and your health care provider must decide
what is a normal HbA1c level for you.
Normal ranges may vary slightly among different laboratories. Talk to your doctor about
the meaning of your specific test results.
What Abnormal Results Mean
Abnormal results mean that your blood glucose levels have been above normal over a
period of weeks to months. If your HbA1c is above 7%, it means that your diabetes
control may not be as good as it should be.
High values mean you are at greater risk of diabetes complications. If you can bring your
level down, you decrease your chances of long-term complications.
Ask your doctor how often you should have your HbA1c tested. Usually, doctors
recommend testing every 3 or 6 months.
Risks
Veins and arteries vary in size from one patient to another and from one side of the body
to the other. Obtaining a blood sample from some people may be more difficult than from
others.
Other risks associated with having blood drawn are slight but may include:
• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)

3. • Infection (a slight risk any time the skin is broken)
References
American Diabetes Association. Standards of medical care in diabetes -- 2009. Diabetes
Care. 2009;32:S13-S61.
Inzucchi SE, Sherwin RS. Type 1 diabetes mellitus. In: Goldman L, Ausiello D, eds.
Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 247.
Inzucchi SE, Sherwin RS. Type 2 diabetes mellitus. In: Goldman L, Ausiello D, eds.
Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 248.

4. What is the HbA1C?
• HbA1c
• Two examples: poor control & good control
• When should the HbA1c be measured
• Illustrated diagramatically
• Comparision of glucose and HbA1c levels
• Large animation
• HbA1c to blood glucose convertor (link)
• Helpful link
The HbA1c
Enlarge Haemoglobin, in your blood, joins up with glucose to form the
chemical called HbA1c
In the blood stream are the red blood cells, which are made of a molecule, haemoglobin.
Glucose sticks to the haemoglobin to make a 'glycosylated haemoglobin' molecule, called
haemoglobin A1C or HbA1C. The more glucose in the blood, the more haemoglobin
A1C or HbA1C will be present in the blood.
Red cells live for 8 -12 weeks before they are replaced. By measuring the HbA1C it can
tell you how high your blood glucose has been on average over the last 8-12 weeks. A
normal non-diabetic HbA1C is 3.5-5.5%. In diabetes about 6.5% is good.
The HbA1C test is currently one of the best ways to check diabetes is under control; it is
the blood test that gets sent to the laboratory, and it is done on the spot in some hospital
clinics. Remember, the HbA1C is not the same as the glucose level.
Coincidentally the glucose/HbA1C numbers for good control are rather similar though in
the UK and Europe: glucose levels averaging 6.5 mmols/l before meals is equivalent to
7% HbA1C (glucose levels are higher after meals) (see below).

5. Two examples
Below are two examples of people who have their HbA1c measured. One is poorly
controlled, one well controlled.
A graph of glucose changes over 9 Here the glucose changes between 5-9.
weeks. The glucose (green This results in an HbA1c level
line) changes between 7-12. of 7% at the end of the 9 weeks.
This results in an HbA1c level Well controlled.
of 10% at the end of the 9
weeks (red line). Poorly
controlled.
When should the HbA1C be measured?
Measure HbA1c
• every 3 months if
trying to improve
• evey 6 months if very
stable
•
If your diabetes is controlled (basically an HbA1C lower than 7%), every 3-6 months.

6. But if the last reading is above 7% and you are in reasonable health, you will need to
achieve a lower level if possible, and the next reading should be sooner. This assumes
you will make changes to improve your control. There is no point in having your HbA1c
measured if you are not trying to achieve good control of your diabetes, although the
level does predict the likelihood of complications from your diabetes.
Your ideal HbA1c depends on your general health, and whether or not you use insulin,
etc, and is discussed here.
Illustrated diagrammatically
Haemoglobin in the blood (red, rectangle) combines with glucose in the blood
(green, circle) to form glycosylated haemoglobin.
This reaction occurs over a 10 week period.
Controlled diabetes, not much glucose,
not much glycosylated Uncontrolled diabetes, more glucose,
haemoglobin much more glycosylated

7. haemoglobin
Glucose levels fluctuate from minute to minute, hour to hour, and day to day. Thus for
hour to hour control, or day to day, a glucose level is the best guide.
The HbA1C level changes slowly, over 10 weeks, so it can be used as a 'quality control'
test.
In diabetes glucoses tend to rise more than usual, dropping with exercise, rising after
food, rising a lot more after sweet food, and can make it hard to control.
For how to lower the HbA1C to achieve better control (and better health in the long
term), see the pages type 1 diabetes/insulin (type2) or type 2 diabetes (no insulin). Good
control produces benefits that lasts 10 years at least (NEJM 2008).
How does your glucose level compare with your HbA1c
HbA1c % Average
blood
glucose level
mmol/l
13 18
12 17
11 15
10 13
9 12
8 10
7 8
6 7
5 5
HbA1c levels by coincidence nearly equate to glucose levels. So an HbA1c level of 10%
means the average glucose level for the previous 10 weeks was 13mmol/l.

8. But at lower levels there is even less difference, so an HbA1c of 7% means the average
glucose level was 8mmols/l.