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Test Code CAFF Caffeine, Serum

Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.

Secondary ID


Useful For

Monitoring caffeine therapy in neonates


Assessing caffeine toxicity in neonates

Method Name

Enzyme Multiplied Immunoassay Technique (EMIT)

Reporting Name

Caffeine, S

Specimen Type


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 28 days
  Ambient  72 hours
  Refrigerated  72 hours

Reject Due To

Gross hemolysis Reject

Clinical Information

Caffeine is used to treat apnea that occurs in newborn infants, the most frequent complication seen in the neonatal nursery.


Caffeine is administered orally (nasogastric tube) as a loading dose of 3 mg/kg followed by a maintenance dose of 1 mg/kg administered once every 24 to 48 hours, depending on the patient's response and the serum level.


In neonates, caffeine has a half-life that ranges from 20 to 100 hours, which is much longer than in adults (typically 4-6 hours) due to the immaturity of the neonatal liver. This requires that small doses be administered at much longer intervals than would be predicted based on adult pharmacokinetics.


The volume of distribution of caffeine is 0.6 L/kg and the drug is approximately 35% protein bound.


Toxicity observed in neonates is characterized by central nervous system and skeletal muscle stimulation and bradycardia. These symptoms are seen in adults at lower levels than in neonates, suggesting that neonates have much greater tolerance to the drug.

Reference Values

Therapeutic: 8.0-20.0 mcg/mL

Critical value: ≥30.0 mcg/mL


Optimal pharmacologic response occurs when the serum level is in the range of 8.0 to 20.0 mcg/mL.


Toxicity in neonates and adults may be seen when the serum level is above 20.0 mcg/mL.

Clinical Reference

1. Ou CN, Frawley VL: Concurrent measurement of theophylline and caffeine in neonates by an interference-free liquid-chromatographic method. Clin Chem 1983;29:1934-1936

2. Nader R, Horwath AR, Wittwer CT: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics Sixth Edition. St. Louis. Elsevier 2018

Day(s) and Time(s) Performed

Monday through Saturday

Analytic Time

Same day/1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CAFF Caffeine, S In Process


Result ID Test Result Name Result LOINC Value
8754 Caffeine, S 3422-3


If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.