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PTD - 240

Test Directory - Gentamicin

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's) with date and time blood sample collected.


On request.

Specific Criteria

For once daily Gentamicin dosing, levels should be taken between 18-24 hrs after the dose.
For multiple daily Gentamicin dosing (please refer to indications in the Trust antibiotic policy) levels should be taken as follows:
a) Pre-dose immediately prior to the drug being given
b) Post-dose 1 hour after dose

Patient Preparation

Once daily Gentamicin is administered at any time of the day, as per clinical indications and subsequent doses will be based on levels.
Multi dose regimens: dosage should be 12 hourly. First assays should be undertaken on the third or fourth doses.

Turnaround Time

Performed on the same day within 2 hours of receipt in the laboratory.


Serum. Plasma is recommended for patients on haemodialysis.


2 ml.


Yellow top (SST) tube or

Paediatric orange top (lithium-heparin)

For patients on haemodialysis, blood in a green top (lithium-heparin) tube is preferred:

Causes for Rejection

Unlabelled sample
Not meeting specific criteria for analysis

Reference Ranges

For once daily regimen:

Pre-dose -    <1.0 mg/L          (multiple dose regime)

For multi-dose regimen:
Pre-dose -    <2.0 mg/L          (multiple dose regime)
Post-dose -    5.0 - 10.0 mg/L (multiple dose regime)

Multi dose for  the treatment of endocarditis patients:

Pre-dose -  <1.0 mg/L   (endocarditis patients)

Post-dose - 3.0 - 5.0 mg/L ( endocarditis patients)

The suggested ranges are for guidance only, these may vary with disease process and the infecting organism, please refer to the appropriate trust protocol.

Lab Handling Processing: Analysed from primary tube and stored at 4C in the cold room (CB23)


Version 1.0 / July 2014                                                                                                            Approved by: Consultant Biochemist