Theophylline, Serum Concentration
This test measures the amount of theophylline, a medication used to treat certain breathing and heart conditions, in your blood serum.
["Your doctor may check this level to ensure you’re taking the right dose of theophylline."]
Key facts at a glance
- LOINC
- 110253-2
- Short code
- Theophylline Msmt SerPl
- Synonyms
- Theophylline Msmt SerPl
- 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 conditions like asthma, chronic obstructive pulmonary disease (COPD), or certain heart rhythms. They may also check it if you have symptoms like rapid heartbeat, nausea, or trouble sleeping, which could indicate too much or too little medication in your system.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. It usually takes a few minutes, and you can resume normal activities afterward.
What the Results Mean
Theophylline levels can vary based on your dose, how you take it, and other health factors. Your doctor will compare your results to guidelines specific to your medication and condition to determine if your dose is appropriate.
Common Reasons for Monitoring
Regular monitoring helps prevent side effects like heart rhythm changes, liver issues, or digestive problems. It also ensures the medication stays effective for managing your breathing or heart condition.
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.
This test is critical for patients on long-term theophylline therapy because the medication can build up in the body over time, leading to toxicity if levels are too high. Low levels may mean the medication isn’t working as intended. Your doctor will adjust your dose based on these results to balance safety and effectiveness.
Short name
Theophylline Level
Frequently asked questions
Why might my doctor want to check my theophylline level frequently?
How long does it take to get my test results back?
Can I stop taking theophylline if my levels seem too low?
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