GLUCOSE TOLERANCE TEST (GTT)

Fasting plasma glucose (measured before GTT) :

< 110 mg/dl Normal 

110 – 125 mg/dl Borderline 

>125 mg/dl Diabetic 

A 1 hour GTT below 180 mg/dl is considered normal 

For a 2 hr GTT with 75 g intake, 

Glucose level <140 mg/dl is normal 

140 -200 mg/dl – impaired glucose tolerance 

>200 mg/dl at 2 hrs - Diabetic

• Glucose Tolerance test measures how well the body cells are able to absorb glucose, or sugar ,after you ingest a given amount of sugar. 75 gm of oral dose is the recommendation by WHO to be used in adults . The dose shall be drunk in 5 minutes. This protocol challenges the person’s body to process the glucose

For Gestational Diabetes (using one step or 2 step approach)

One step approach

• After a fasting glucose level is measured, a woman is given 75 gm dose of glucose to drink and her glucose levels are measured at 1 hour and 2 hours after the dose. Only one of the values needs to be above a cut off value for diagnosis.

2 Step approach 

• At 24-28 weeks - 1 hr venous glucose measurement following 50 gm oral glucose solution (GLUCOSE CHALLENGE TEST), followed by a 3 hr 100 gm Oral glucose tolerance test , if positive. 
• Diagnosis of gestational diabetes mellitus is based on 2 abnormal values on the 3 hour OGTT(measured at 1 hr, 2 hr and 3 hr)
• Post 1 hr 50 gm GCT : 140 mg/dl

3 hrs OGTT

• Fasting - 95 mg/dl
• 1 hours : 180 mg/dl
• 2 hours : 155 mg/dl
• 3 hours : 140 mg/dl

• When a person is aged 45 or older
• When a person of any age has risk factors(Overweight, physically inactive, PCOS , High BP , Low HDL level and high Triglyceride level, h/o cardio vascular disease)
• When there is s/s of high Glucose ( Increased Thirst, frequent urination , fatigue , blurred vision , slow healing wounds or infections )

• Acute stress
• Diabetes
• Acromegaly
• Chronic kidney disease
• Hyperthyroidism
• Pancreatic cancer

• Adrenal insufficiency
• Liver disease
• Hypothyroidism
• Renal failure 
• Insulinoma