Preferred Sample Type


Suitable Specimen Types

  • Serum
  • EDTA Plasma
  • Li Hep Plasma
A minimum of 50 µl of plasma/serum is required.

Specimen Transport

First class post

Sample Processing in Laboratory

Place sample in toxicology rack.

Sample Preparation

None required

Turnaround Time

3 days

Sample Stability

Keep refrigerated. 4 degrees.


General Information

Caffeine is a weakly basic alkaloid that occurs naturally in coffee and cocoa beans, kola nuts and tea leaves in amounts of up to 2% by weight. It is a mild central nervous system stimulant that also produces diuresis, myocardial and respiratory stimulation and coronary vessel dilation. Caffeine is frequently administered orally in analgesic mixtures, migraine remedies and antisoporific preperations in amounts of 32 -200 mg; it is occasionally used to reverse central depression in adults by i.m injection of 0.5 – 1.0 g or apnea in premature infants by i.v injection of 15 – 20 mg/kg.

Caffeine in excess can cause flushing or chills, irritability, loss of appetite, weakness, tremor, tachycardia, vomiting, fever, convulsions, cardiac arrhythmias, coma and death.

Patient Preparation

Since daily doses and an extended half-life in premature babies generally result in stable drug levels, the sample collected is usually a random level, not a trough level.


Caffeine measured by HPLC-DAD.

Serum from gel tubes (yellow top) will NOT be analysed.

Reference Range

Therapeutic range: 4.0 – 10.0 mg/L. Toxic effects are associated with blood concentrations greater than 15 mg/L. (Schulz et al. Critical Care 2012, 16:R136).


  • EQA Scheme?: Yes

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HTA licence number is 12366

Protection of Personal Information – Laboratory Medicine comply with the Trust Data Protection Policy and have procedures in place to allow the Directorate and it’s employees to comply with the Data Protection Act 1998 and associated best practice and guidance.

The Trust Laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital were awarded UKAS (United Kingdom Accreditation Service) accreditation to the internationally recognised ISO 15189 standard in May 2015. For a list of accredited tests and other information please visit the test database
Tests not appearing on this scope are either under consideration or in the process of accreditation and so currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235