Download What does “fasting” mean? Do I need to fast for my blood test? How

What does “fasting” mean?
Several tests require that the patient refrains from eating for a period of time prior to the test.
“Fasting” means nothing to eat (including gum and candy), drink, or smoke for at least 8
hours. You are permitted to drink water. Medications should continue to be taken as
scheduled unless advised otherwise by your physician.
Do I need to fast for my blood test?
Some of the more common tests that require fasting are listed below. Your doctor may have
ordered a less common test for which fasting is either required or preferred, or requires some
other preparation prior to the sample collection.
Common tests which require fasting:
Some tests for which fasting is preferred :
• Cryoglobulin
• Gastrin
• Glucose Fasting
• Glucose Tolerance (includes Gestational
Diabetes Confirmation)
• Lactose Tolerance
• Lipid Profile
(Cholesterol, Triglyceride, HDL, LDL)
• Cholesterol, Triglyceride
• D-Xylose Tolerance
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Homocysteine
Insulin
Iron and Iron Profile
Growth Hormone
Parathyroid Hormone
How long must I fast?
If your test states fasting is required or preferred, fast for 8 hours prior to the test unless the
instructions specifically state otherwise.
Fasting Glucose
8 -10 hour fast prior to test
Lipid Profile:
Cholesterol/Triglyceride/HDL/LDL
12-14 hour fast prior to test
Glucose Tolerance Test:
Gestational Diabetes Screen
Fasting is NOT required.
Gestational Diabetes Confirmation
Non-Gestational GTT
For 3 days prior, eat regular meals with
adequate carbohydrate intake. Fast 10
hours prior to the test.
Gestational Diabetes
Gestational Diabetes Screening should be performed between the 24th and 28th week of
gestation. The patient should eat as normal prior to the test and must not be fasting.
• Arrive at the laboratory at any time during normal hours of operation.
• Eat normal meals prior to the test, but avoid food items containing a high sugar load,
e.g. “Slurpee”.
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You will be given a 50 gm glucose drink to consume. A blood test will be scheduled to
be collected 1 hour after completion of the drink. You are required to remain in the Lab
Outpatient area while waiting to have your specimen taken.
If you experience any discomforting symptoms such as nausea, dizziness or sweating,
please make the laboratory staff aware right away. Adverse reactions will be noted and
the ordering physician will be informed.
Based on the results of this test, your doctor may want you to have the Gestational
Diabetes Confirmation test. You must follow the same preparation instructions as for
the Glucose Tolerance Test.
Glucose Tolerance Test
You should arrive fasting and are required to remain in the Laboratory Outpatient waiting area
for the duration of the test. The oral glucose load for adults is 75 grams and the child dose is
1.75 gm/kg of body weight up to a maximum of 75 grams.
• You are required to have no caloric intake for at least 10 hours prior to the blood
collection. This includes NO gum, candy, coffee, tea or diet soft drinks. Water is
permissible.
• You should also refrain from smoking during the fast.
• Arrive at the laboratory at any time during normal hours of operation.
• A fasting blood sample will be collected.
• You will be given a 75 gm glucose drink to consume. Timing for the test will begin upon
completion of the drink.
• You are required to remain in the Lab Outpatient area while waiting to have your
remaining blood samples collected.
• If you experience any discomforting symptoms such as nausea, dizziness or sweating,
please make the laboratory staff aware right away. Adverse reactions will be noted and
the ordering physician will be informed. Depending on the severity of the symptoms,
testing may be stopped.
• Blood specimens will be drawn according to which test is requested:
 Glucose Tolerance (non-pregnant):
o Fasting
o 2 hr post 75 gm dose
 Glucose Tolerance (gestational):
o Fasting
o 1 hr post 75 gm dose
o 2 hr post 75 gm dose
Updated: 27Feb13