Glucose Tolerance

non-pregnant:              GTTNP
pregnant:                    GTTPREG
pregnant 3 hour:          GTTPREG3
pathologist approval:    GTTPA
children(<17y):           GTTCHILD

By appointment only.
Community patients: may contact Patient Service Centre of choice.
Hospital patients: nursing unit to book appointment with on site lab.

Pediatric patients <17y are given a 1.75g dose/kg body weight.

Greater than 2 hour glucose tolerance on non-pregnant adults has restricted clinical indications and requires review and approval by CLS Medical & Scientific Staff.  Contact LIC at 770-3600 for Pathologist On Call information.

1 x 5 mL light green (mint) top PST tube for each timed specimen.  Gold top SST tube is also acceptable.

0.2 mL heparinized plasma or serum
Pediatric: 0.2 mL whole blood

PSC: Patient instruction sheet (form #CH3002) may be given to patient.

Procedure takes 2 or more hours. 

Reference Interval

Fasting Specimen: 3.9-6.1 mmol/L

Interpretation

Non-Pregnant Adults:

• If fasting glucose greater or equal to 7.0 mmol/L or 2 h PC greater or equal to 11.1 mmol/L, diagnostic of diabetes mellitus. 
• If fasting glucose less than 7.0 mmol/L and 2 h PC between 7.8 and 11.0 mmol/L, indicates impaired glucose tolerance. 
• Please see clinical practice guidelines www.diabetes.ca/cpg2003

Children <17y:

• The diagnostic criteria for diabetes in children are the same as for adults. Please see clinical practice guidelines www.diabetes.ca/cpg2003

Pregnant:     

• If one of three values is elevated, diagnosis is impaired glucose tolerance of pregnancy. 
• If two or three values are elevated, diagnosis of gestational diabetes mellitus has been established. 
• Please see clinical practice guidelines www.diabetes.ca/cpg2003

Hypoglycemia:

Documentation of reactive hypoglycemia requires demonstration of Whipple’s Triad:

•  Symptoms
•  Alleviation by glucose
•  Plasma glucose less than 2.8 mmol/L