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Therapeutic Drug Levels

Theophylline Level

Normal range 10–20 µg/mL (56–111 µmol/L SI). Specimen: Serum.

Also known as: aminophylline level.

10–20 µg/mLCritical: read below

Reference range

Conventionalµg/mL
1020
SIµmol/L
56111
SpecimenSerum
Conventional range10–20 µg/mL
SI range56–111 µmol/L
Conversion factor×5.55 (conventional → SI)
Critical value> 20 µg/mL (nausea, tachycardia, seizures)
PanelTherapeutic Drug Levels

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What is the normal range for Theophylline Level?

The standard teaching reference range for Theophylline Level is 10–20 µg/mL in conventional units, or 56–111 µmol/L in SI units. This value is measured in serum.

A commonly taught critical (panic) value is > 20 µg/mL (nausea, tachycardia, seizures). Critical results are reported to the provider immediately under your facility's policy.

Source: Adult reference values compiled from Pagana & Pagana, Mosby's Diagnostic and Laboratory Test Reference, and Fischbach & Dunning, A Manual of Laboratory and Diagnostic Tests. Reference ranges vary by laboratory, method, age, sex, and population — always use the range printed on the actual result.

Above the range

Common causes of a high Theophylline Level

  • Excess dosing
  • Liver disease
  • Heart failure
  • Interactions (cimetidine, ciprofloxacin)

Below the range

Common causes of a low Theophylline Level

  • Smoking (increases clearance)
  • Nonadherence

At the bedside

Nursing considerations

  • Watch for tachyarrhythmias, nausea, and seizures as levels rise; narrow therapeutic window.

Study aid

Your notes on Theophylline Level

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