Glucose Tolerance Test
|Why is this test done?||This test is used to screen for diabetes, gestational diabetes or glucose intolerance. It is a useful part of diabetes diagnostic when blood glucose levels are borderline. It is used to evaluate people with unexplained generalized weakness, eye problems or kidney problems.|
|How to prepare:||
|Associated Tests:||This test is rarely done by itself. Glycosylated hemoglobin, fasting and 2h postprandial (after a meal) blood glucose are usually measured as well as the presence of albumin, glucose or ketone bodies in urine.|
A first blood test on an empty stomach is made, then you will have to drink, within 5 minutes, a 300 mL glass of water mixed with 75 to 100 g of glucose. Then your blood glucose level will be measured 1 and 2 hours later by doing a blood test. The test is used to evaluate the body's ability to managed sugar from the diet.
What does an abnormal test result mean?
If the result is too high
This could indicate that the person suffers from diabetes mellitus or a pancreatic, renal or hepatic disorder.
If the result is too low
Certain hormonal problems can explain lower results.
Factors that can affect the result of the test
Non-respect of the fasting period or other preparatory measures may explain erroneous results. Certain drugs can affect blood glucose levels: some lowers it, and are used to that effect. Others however are used to treat another problem and cause hyperglycemia as an adverse effect. Such drugs include:
- ethacrynic acid (Edecrin™)
- corticosteroids (e.g. prednisone (Deltasone™))
- fenoterol (Berotec™)
- furosemide (Lasix™)
- lithium (Carbolith™)
- orciprenaline (Alupent™)
- pentamidine (Pentacarinat™)
- phenytoin (Dilantin™)
- pseudoephedrine (Sudafed™)
- salbutamol (Ventolin™)
- terbutaline (Bricanyl™)
- thiazide diuretics (hydrochlorothiazide (Hydrodiuril™), indapamide (Lozide™), etc)
Emotions, stress, fever, infections, thyroid disorders and cirrhosis all affect blood glucose levels.
What you need to know before the test
Before going for blood tests, a procedure or other exam, it is best to always bring a list of all the drugs you take (prescription, OTC and natural health products). Unless told otherwise, you should take your medication as usual on the day of the test. When in doubt, ask your pharmacist for more information.
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.