Oral Glucose Tolerance Test
How It Feels
You may find it hard to drink the
extremely sweet glucose liquid. Some people feel sick after drinking the
glucose liquid and may vomit. Vomiting may prevent you from completing the test
on that day.
The blood sample is taken from a vein in your arm. An
elastic band is wrapped around your upper arm. It may feel tight. You may feel
nothing at all from the needle, or you may feel a quick sting or pinch.
You may feel faint from having several blood samples taken in one day.
But the amount of blood taken will not cause significant blood loss or
Some people's blood glucose levels drop very low
toward the end of the test. But some people feel like their sugar levels
are low, when their levels actually are not low. Symptoms of low blood glucose
include weakness, hunger, sweating, and feeling nervous or restless. If you
develop these symptoms during the test, you may have your sugar level checked
quickly with a glucose meter. If your level is very low, the test will be
There is very little risk of a problem from having blood
drawn from a vein.
- You may develop a small bruise at the puncture
site. You can reduce the risk of bruising by keeping pressure on the site for
several minutes after the needle is withdrawn.
- In rare cases, the
vein may become inflamed after the blood sample is taken. This condition is
called phlebitis and is usually treated with a warm compress applied several
- Continued bleeding can be a problem for people with
bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning
medicines can also make bleeding more likely. If you have bleeding or clotting
problems, or if you take blood-thinning medicine, tell your health professional
before your blood is drawn.
oral glucose tolerance test (OGTT) measures the body's
ability to use a type of sugar, called glucose, that is the body's main source
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Normal glucose tolerance test values
| 75 g of
glucose|| Fasting:||Less than or equal to 100 milligrams per deciliter (mg/dL) or 5.6 millimoles per liter (mmol/L)1|
| 1-hour:||Less than 184 mg/dL or less than 10.2 mmol/L2|
| 2-hour:||Less than 140 mg/dL or less than 7.7 mmol/L2|