Theophylline (Serum/Plasma Mass Concentration)
This test measures the amount of theophylline, a medication used to treat breathing problems like asthma or chronic obstructive pulmonary disease (COPD). It helps doctors check if your dose is working properly.
["Your theophylline level helps ensure your medication is at the right amount for your condition."]
Key facts at a glance
- LOINC
- 35596-6
- Short code
- Theophylline SerPl Scn-mCnc
- Synonyms
- Theophylline SerPl Scn-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- 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
- Method
- screen
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test if you’re taking theophylline to manage breathing issues. They might check your level to adjust your dose, monitor for side effects, or ensure it’s working as intended. This is especially important if you have conditions like asthma, COPD, or heart rhythm problems.
What to Expect Before the Test
No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. It usually takes a few minutes. If you’re on a regular theophylline regimen, your level may be checked at different times (e.g., before or after doses) to get the most accurate reading.
What the Results Mean
Theophylline levels can vary based on how your body processes the drug, your diet, and other medications you take. Your doctor will compare your result to your usual range and discuss it with you. Very high or low levels can cause side effects or reduce the drug’s effectiveness.
Common Side Effects to Watch For
High levels of theophylline can cause nausea, headaches, rapid heartbeat, or trouble sleeping. Low levels might mean your dose isn’t working well. If you experience these symptoms, talk to your doctor right away.
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 to relieve symptoms of asthma and COPD. Regular monitoring helps prevent toxicity (overdose) or insufficient effectiveness. Levels may fluctuate due to factors like smoking, liver function, or other medications, so your doctor will guide adjustments based on your specific situation.
Short name
Theophylline Level
Frequently asked questions
Why might my theophylline level be checked at different times?
What if my theophylline level is too high?
Do food or other medications affect my theophylline level?
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