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Epic Test Code LAB26 Gentamicin, Trough

Performing Location(s)





Quantitative analysis for Gentamycin

Specimen Type

Serum or Plasma

Preferred Container

Gold or Red Top

Alternate Container

Green top

Storage Requirements

Sample tubes should be centrifuged within 2 hour of collection followed by transfer of the serum (red or gold top) or plasma (green top) to a labeled plastic, aliquot tube.

See Causes of Rejection for temperature requirements.

Transportation Needs

Deliver specimen to the laboratory within 1 hour of collection. If not possible see “Storage Requirements”

Causes for Rejection

Mislabeled or unlabeled specimen
Less than 50% draw for Vacutainer tubes
 >  6 weeks refrigerated (Serum  tubes are routinely stored at the lab for only 7 days therefore, an add-on may not be possible after 7 days) 
 > 24 hours room temperature
> 6 months Frozen
Hemolysis > 800 mg/dL HgB
Lipemia > 750 mg/dL Trig
Bilirubin > 30 mg/dL Bili

Days of Analysis


Additional Information

Collection Guideline:

Obtain a baseline creatinine and repeat at 1-3 day intervals.
Begin monitoring after steady state is achieved (usually 3-4 doses).

Monitor at least one peak (60-90 min after IM or 30-60 min IV) and one trough (within 30 min of next dose).

Repeat trough measurements at 3-4 day intervals or sooner if warranted by clinical status.
Base frequency of monitoring on changes in dose and patient symptoms

Perform urinalysis by day 3 and repeat as necessary to assess early proximal tubular dysfunction.

Available STAT


Reference Values

Level Units Therapeutic Range High Critical Value
Random ug/mL 2 - 8 >18
Peak ug/mL 4 - 8 >18
Trough ug/mL < 2 >2


Therapeutic gentamicin concentrations vary significantly depending on the individual patient. A range of 4.0-8.0 µg/mL [8.64-17.28 µmol/L] for peak drug levels indicates effective plasma or serum levels for many patients; however, some individuals are best treated at concentrations outside this range. Although it has not yet been established exactly what specimen concentration is toxic, minimal values in excess of 2 µg/mL [4.32 µmol/L] for longer than 10 days have been associated with toxicity.


Aminoglycosides structurally similar to gentamicin (e.g. netilmicin, sagamicin, and sisomicin) may significantly cross-react with this method. Therefore, GENT cannot reliably be used for patients receiving these antibiotics separately or in combination with gentamicin.


Beckman AU/Dx Series

CPT Code


Last Updated


Minimum Volume to Submit for Testing

0.5 mL Serum or Plasma

  • Multiple test can be performed from this volume. For question please contact the lab at 547-3975.