Theophylline Concentration (Serum)
This test measures the amount of theophylline, a medication used to treat asthma and other breathing disorders, in your blood.
["Theophylline levels help ensure you’re taking the right dose for your condition."]
Key facts at a glance
- LOINC
- 108522-4
- Short code
- Theophylline Msmt Ur
- Synonyms
- Theophylline Msmt Ur
- Category
- chemistry
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 10
- Ref high
- 20
- Critical range
- — – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test if you’re taking theophylline (such as Theophylline, Theo-Dur, or Slo-Bid) to check if your blood levels are within the safe range. It’s also used to monitor long-term treatment or adjust your dose if needed.
What Does This Test Tell You?
High levels of theophylline can cause side effects like nausea, rapid heartbeat, or even serious health risks. Low levels might mean your medication isn’t working as intended. This test helps balance your dose to avoid these issues.
How Is the Test Done?
A blood sample is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed using a sensitive method to measure theophylline concentration.
What to Expect Before the Test
No special preparation is needed, but tell your doctor about any other medications you’re taking, as some can affect theophylline levels.
Reference range
Therapeutic: 10-20 mcg/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Theophylline is a bronchodilator used primarily for managing chronic obstructive pulmonary disease (COPD) and asthma. Optimal levels help prevent symptoms like wheezing or shortness of breath while minimizing side effects. Regular monitoring is critical because the medication can build up in the body over time, especially in people with kidney issues or who take other medications that interact with it.
Short name
Theophylline Level
Frequently asked questions
What Are Common Side Effects of High Theophylline Levels?
How Often Should I Have This Test?
Can I Drink Coffee or Eat Before the Test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy