Theophylline Peak Concentration (Serum/Plasma)
This test measures the highest blood level of theophylline, a medication used to treat certain breathing and heart conditions. It helps doctors monitor how well your body is handling the drug over time.
["This test ensures your theophylline levels stay safe and effective for managing your condition."]
Key facts at a glance
- LOINC
- 32115-8
- Short code
- Theophylline Peak SerPl-sCnc
- Synonyms
- Theophylline Peak SerPl-sCnc
- 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 This Test Matters
Theophylline is a medication often prescribed for conditions like asthma, chronic obstructive pulmonary disease (COPD), or heart rhythm disorders. Keeping levels too high can cause side effects, while levels that are too low may mean the medication isn’t working properly. This test helps prevent these issues by checking your peak concentration right after you take the dose.
What to Expect Before the Test
No special preparation is needed for this test. You may have a small needle inserted into your arm or vein to draw blood. The process usually takes a few minutes. If you’re on a theophylline infusion (like through an IV), your provider may check your blood level at a specific time during treatment.
What the Results Mean
Results from this test help your healthcare provider adjust your medication dose if needed. They’ll compare your peak level to your lowest level (trough) and any other test results to find the right balance for your condition. Always follow your provider’s guidance on interpreting these results.
Common Reasons for Testing
Your doctor might order this test if you’re on long-term theophylline therapy, if you’re experiencing side effects like nausea, headaches, or rapid heartbeat, or if you’re having trouble controlling your symptoms. It’s also used to check if the medication is working as intended.
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 narrow therapeutic window medication, meaning small changes in blood levels can lead to serious side effects or reduced effectiveness. Peak levels help identify whether your dose is too high or too low. Regular monitoring is especially important if you have liver or kidney issues, take other medications that interact with theophylline, or have certain health conditions like heart disease.
Short name
Theophylline Peak Level
Frequently asked questions
How often should I expect this test?
What happens if my theophylline levels are 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