Theophylline µmol/L → µg/mL
Convert theophylline from µmol/L to µg/mL
Sources last checked: 2026-11-03
Theophylline µmol/L → µg/mL
Convert theophylline from µmol/L to µg/mL
Converts units only; reference ranges depend on the laboratory, the assay and the patient.
What is the Theophylline µmol/L → µg/mL?
This converter turns a theophylline concentration from µmol/L, used by some SI-reporting laboratories and in parts of the literature, into µg/mL (identical to mg/L), the unit most laboratories and dosing references use. It divides by 5.551 (equivalent to multiplying by about 0.1801), derived from the molar mass of theophylline, 180.16 g/mol.
When to use it
- Reading a theophylline level in µmol/L from an SI-reporting letter or study
- Comparing serial levels from laboratories that report in different units
- Assessing a suspected overdose against toxicology references written in mg/L
When not to use it
- Caffeine or other methylxanthines, which have different molar masses
- Interpreting the value: target ranges and toxicity thresholds depend on the clinical context, the guideline and whether the exposure is acute or chronic
How it is calculated
Theophylline (µg/mL) = theophylline (µmol/L) ÷ 5.551
Clinical pearls and limitations
- Converts units only; reference ranges depend on the laboratory, the assay and the patient.
- Dividing by 5.551 is the same as multiplying by 0.1801; dividing by 5.5 gives a quick estimate.
- µg/mL and mg/L are numerically identical, so a result in mg/L can be compared directly.
- In modified-release overdose, absorption can be prolonged and the level may keep rising; serial levels are more informative than a single value.
- Chronic toxicity can cause seizures and arrhythmias at lower levels than acute overdose; the level must be read alongside the clinical picture, potassium and glucose.
Frequently asked questions
How do I convert theophylline from µmol/L to µg/mL?
Divide by 5.551. For example, 64 µmol/L ÷ 5.551 = 11.5 µg/mL.
What is 1 µmol/L theophylline in µg/mL?
1 µmol/L corresponds to 0.18 µg/mL, because 180.16 g/mol × 1 µmol/L = 180.16 µg/L.
Why do theophylline levels vary so much between patients on the same dose?
Theophylline is hepatically metabolised, and its clearance is altered by smoking status, heart failure, liver disease, age, fever and many drug interactions.
Evidence and guidelines
Have a follow-up question?
Medelix answers clinical questions from current guidelines and studies — every statement with its source.
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<p><a href="https://medelix.ai/en/calculators/theophylline-umol-l-to-ug-ml">Theophylline µmol/L → µg/mL calculator by Medelix</a></p>For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.