Test Category: Biochemistry
Investigation Name:Glucose Tolerance Test
Alias or Abbreviation:GTT/OGTT
Accreditation:UKAS Accredited ISO15189:2022 On scope
Intro:
The Glucose Tolerance Test (GTT) is not recommended for routine screening for diabetes mellitus. Consider requesting a GTT when fasting plasma glucose is repeatedly 6.1–6.9 mmol/L and HbA1c is either unsuitable for diagnosis or <48 mmol/mol.How to request/book a GTT:
- Process is for non-pregnant adults only. For pregnant patients and paediatric patients, GTTs are arranged via the relevant specialist services.
- Sandwell/Walsall/Wolverhampton general practice patients: 1) Request in ICE. 2) Print out form and stickers – staple together. 3) Send to the laboratory via routine courier FAO Duty Biochemist. 4) Duty Biochemist reviews request where it is either passed to an administrator to arrange an appointment, or a report will be sent out informing that the request has been rejected.
- Dudley patients: Email dgft.chemicalpathologysecretaries@nhs.net to arrange an appointment. Provide patient details (name, NHS number, contact details), the requesting clinician, and indication for the request.
Contact the Duty Biochemist at rwh-tr.bcpsdutybiochemist3@nhs.net for queries.
Pathology Laboratory:Clinical Chemistry/ Biochemistry
Requestable Seperately?Yes
Minimum Sample Volume:1 mL at each time point
Expected Turnaround Time:1 working day from receipt
Test Code:OGTT
Sample Type:
EDTA Fluoride Oxalate Tube (Grey top)Complex Reference Range:Diabetes: Fasting glucose >= 7.0 mmol/L or 2hr glucose >= 11.1 mmol/L (>= 7.8 mmol/L in pregnancy).
Impaired glucose tolerance: 2 hr glucose 7.8-11.0 mmol/L
Impaired fasting glucose: 6.1-6.9 mmol/L (>= 5.6 mmol/L in pregnancy
Referred to Another Laboratory?No
UKAS Reference Number:8663
