Theophylline (Mass Concentration in Serum/Plasma)
This test measures the amount of theophylline, a medication derived from tea leaves, in your blood. Theophylline is used to treat breathing problems like asthma or chronic obstructive pulmonary disease (COPD).
["This test helps monitor your medication levels to ensure they’re safe and effective."]
Key facts at a glance
- LOINC
- 4049-3
- Short code
- Theophylline SerPl-mCnc
- Synonyms
- Theophylline SerPl-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
- 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. Regular testing helps prevent side effects, such as rapid heart rate or nausea, by ensuring your medication stays within a safe range.
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 blood. It usually takes a few minutes. If you’re on a long-term medication like theophylline, your provider may schedule tests at regular intervals to check your levels.
What the Results Mean
Results are typically reported in micrograms per milliliter (mcg/mL). Your provider will interpret the results based on your medical history, symptoms, and other medications you’re taking. Too much or too little theophylline can affect how your body works.
Possible Side Effects and Risks
The test itself is generally safe, but you might feel slight discomfort or bruising at the injection site. Rarely, blood tests can cause allergic reactions or infections. If you have a history of bleeding disorders, let your provider know before the test.
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 medication that can have a narrow therapeutic window. High levels may cause side effects like heart rhythm changes, seizures, or vomiting, while low levels may mean the medication isn’t working properly. Regular monitoring helps balance safety and effectiveness, especially in people with kidney issues or those taking other medications that interact with theophylline.
Short name
Theophylline Level
Frequently asked questions
How often should I get this test?
What does a ‘high’ or ‘low’ theophylline level mean?
Can I eat or drink before this 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