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 monitor your dose to ensure it’s effective and safe.
["Your theophylline level helps prevent side effects while keeping your breathing under control."]
Key facts at a glance
- LOINC
- 21559-0
- Short code
- Theophylline Gast-mCnc
- Synonyms
- Theophylline Gast-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84484
- SNOMED
- 302774002
- 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 (a bronchodilator) to manage conditions like asthma or COPD. Regular checks help adjust your medication to avoid too much or too little in your bloodstream.
What to Expect Before the Test
No special preparation is needed. You’ll likely have a small needle inserted into your arm or vein to draw blood. If you’re on a continuous IV infusion, your provider may check levels at specific intervals.
What the Test Results Mean
Results are compared to a general range to guide your treatment. Too high or too low levels can affect how well your medication works or cause side effects like nausea, rapid heart rate, or trouble sleeping.
Possible Side Effects of Theophylline
Common side effects from too much theophylline include headaches, upset stomach, or restlessness. Rarely, very high levels can cause serious heart rhythm issues. Your doctor will adjust your dose based on your test results.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is critical for managing theophylline therapy to balance effectiveness and safety. Low levels may mean your medication isn’t strong enough, while high levels could indicate toxicity or improper dosing. Regular monitoring helps prevent complications.
Short name
Theophylline Level
Frequently asked questions
Why do I need this test regularly?
What happens if my theophylline level is too high?
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