Caffeine, Serum or Plasma

CPT: 80155
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Test Details


  • Cafcit®
  • Energets
  • No Doz® Maximum Strength
  • Vivarin®


Monitor caffeine concentration in newborns receiving theophylline or caffeine.

Half-life elimination: Neonates 72 to 96 hours, Children >9 months and Adults: 5 hours

Time to peak serum, oral: Within 30 minutes to 2 hours


Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

Therapeutic: 3.0−15.0 μg/mL

• Neonatal apnea: 8−14 μg/mL

• Infant (<1 year): 8−20 μg/mL

Critical Value

Potentially toxic: >50.0 μg/mL

Additional Information

Theophylline is used to treat neonatal apnea. Unlike its metabolism in adults, theophylline in neonates is extensively metabolized to caffeine. Plasma elimination half-life in adults is three to six hours. In neonates, caffeine has a half-life of 30 hours. Caffeine overdoses are rare. The clinical presentation is similar to that of theophylline.

Specimen Requirements


Serum or plasma


1 mL

Minimum Volume

0.3 mL


Red-top tube, lavender-top (EDTA) tube, or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.


Transfer separated serum or plasma to a plastic transport tube.

Storage Instructions

Room temperature

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Gel-barrier tube

Clinical Information


Drug Information Handbook. 24th ed. Hudson, OH: Wolters Kluwer Clinical Drug Information, Inc; 2015; 319-321.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
071258 Caffeine, Serum 3422-3 071262 Caffeine, Serum ug/mL 3422-3

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