What is a blood sugar test?
A blood sugar test is a
procedure that measures the amount of sugar, or glucose, in your blood. Your
doctor may order this test to help diagnose diabetes. And people with diabetes can
use this test to manage their condition.
Blood sugar tests provide
instant results and let you know the following:
- your diet or
exercise routine needs to change
- your diabetes medications
or treatment is working
- your blood
sugar levels are high or low
- your overall
treatment goals for diabetes are manageable
Your doctor may also order
a blood sugar test as part of a routine checkup. Or to see if you have diabetes
or prediabetes, a condition where your blood sugar levels are higher than
Your risk for diabetes increases
if any of the following factors are true:
- you are 45 years
old or older
- you are
- you don’t
- you have high
blood pressure, high triglycerides, or low good cholesterol levels (HDL)
- you have a
history of gestational diabetes or giving birth to a baby who weighed over 9
- you have a
history if insulin resistance
- you are Asian,
African, Hispanic, Pacific Islander, or Native American
- you have a
family history of diabetes
Checking your blood sugar
levels can be done at home or at a doctor’s office. Read on to learn more about
blood sugar tests, who they are for, and what the results mean.
does a blood sugar test do?
Your doctor may order a blood sugar test to see if you have diabetes
or prediabetes. The test will measure the amount of glucose in your blood.
Your body takes carbohydrates found in foods like grains and fruits
and converts them into glucose. Glucose, a sugar, is one of the body’s main
sources of energy.
For people with diabetes, a home test helps monitor blood sugar levels.
Taking a blood sugar test can help determine your blood sugar level to see if
you need to adjust your diet, exercise, or diabetes medications.
Low blood sugar (hypoglycemia) can lead to seizures or a coma if left
untreated. High blood sugar (hyperglycemia) can lead to ketoacidosis, a
life-threatening condition that’s often a concern for those with type 1
diabetes. Ketoacidosis occurs when your body starts using only fat for fuel.
What are the risks and
side effects of a blood sugar test?
A blood sugar test has low
to no risks or side effects.
You may feel soreness,
swelling, and bruising at the puncture site, especially if you’re drawing blood
from a vein. This should go away within a day.
Types of blood sugar
You can take a blood sugar
test two ways. People who are monitoring or managing their diabetes use a
glucometer, which pricks your finger, for daily testing. The other method is drawing
Blood samples are
generally used to screen for diabetes. Your doctor will order a fasting blood
sugar (FBS) test, which measures your blood sugar levels, or a glycosylated
hemoglobin. Or your doctor will order a hemoglobin A1C test, which reflects
your blood sugar levels over the last 90 days. The results will show if you
have prediabetes or diabetes.
When to test blood sugar
When and how often you should test your blood sugar
depends on the type of diabetes you have and your treatment.
For type 1 diabetes
According to the American
Diabetes Association (ADA), if you’re managing type 1 diabetes with multiple dose
insulin or an insulin pump, you’ll want to monitor your blood sugar before:
- eating a meal
- critical tasks
like driving or babysitting
High blood sugar
You’ll want to check your blood sugar levels if you
have diabetes and feel increasing thirst and the urge to urinate. These could
be symptoms of high blood sugar and you may need to modify your treatment
If your diabetes is well-controlled but you still
have these symptoms, it may mean you’re getting sick or that you’re under
Exercising and managing your carbohydrate intake
may help with lowering your blood sugar levels. If these changes don’t work,
you may need to meet with your doctor to decide how get your blood sugar levels
back into target range.
Low blood sugar
Check your blood sugar levels if you feel any of
the following symptoms:
- sweaty or
- irritated or
- lightheaded or
- hungry and
- tingly or numb
in the lips or tongue
stubborn, or sad
Some symptoms like delirium, seizures, or
unconsciousness can be symptoms of low blood sugar or insulin shock. Those on
daily insulin injections should ask their doctor about glucagon, a prescription
medicine that can help if you’re having a severe low blood sugar reaction.
You can also have low blood sugar and show no
symptoms. This is called hypoglycemia unawareness. If you have a history of
hypoglycemia unawareness, you may need to test your blood sugar more often.
Some women develop gestational diabetes during
pregnancy. This is when hormones interfere with the way your body uses insulin.
It causes sugar to accumulate in the blood.
Your doctor will recommend testing your blood sugar
regularly if you have gestational diabetes. This is to make sure that your
blood glucose level is within a healthy range. Gestational diabetes usually
goes away after childbirth.
Home testing may be unnecessary
if you have type 2 diabetes and have a diet- and exercise-based treatment plan.
Or if you are taking medications that aren’t associated with low blood sugar.
How is a blood
sugar test administered?
To get a sample, your
doctor will insert a needle into your vein and draw blood. Your doctor will ask
you to fast for 12 hours before the FBS test. You don’t need to fast before the
You can take blood sugar
tests at home with a glucometer. The exact steps of finger stick glucose meter
tests vary depending on the type of glucose meter. Your home kit will have instructions.
The procedure involves
pricking your finger and putting the blood on a glucose meter strip. The strip is
usually already inserted into the machine. Your results will show on the screen
in 10 to 20 seconds.
glucose monitoring (CGM)
You can also wear a device
for continuous glucose monitoring (CGM). The glucose sensor is inserted under
the skin and reads the sugar in your body tissue continuously. It alerts you
whenever your blood sugar is too low or too high.
The sensor can last
several days to a week before it needs to be replaced. You’ll still have to
check your blood sugar with a meter twice a day to calibrate your CGM.
CGM devices aren’t as
reliable for acute problems like identifying low blood sugar levels. For the most
accurate results you should use your glucometer.
What do the results of the blood sugar
Depending on your
condition and the timing of your test, your blood sugar levels should be in the
target ranges listed below.
Your doctor will provide a
more specific target range for your blood sugar levels, depending on the
- how long
you’ve had diabetes
- presence of
- overall health
Tracking your blood sugar
levels is one way to take control of your diabetes. You may find it helpful to
log your results in a journal or app. Trends like continuously having levels that
are too high or too low may mean adjusting your treatment for better results.
The table below shows what
your blood sugar test results mean:
Your doctor will be able
to help create a treatment plan if your results suggest prediabetes or