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Theophylline Concentration (Mass Concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of theophylline, a medication used to treat asthma and other breathing-related conditions, in your blood.

Quick summary

["Knowing your theophylline level helps ensure your medication is working safely at the right dose."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
13581-4
Short code
Theophylline CSF-mCnc
Synonyms
Theophylline CSF-mCnc
Category
chemistry
Sample
csf
Container
Sterile tube
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
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you’re taking theophylline (a bronchodilator) to check if your dose is appropriate. It’s also used to monitor levels in people with certain heart conditions or breathing disorders.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into a vein (usually in your arm) to draw blood. The process is quick and typically causes only minor discomfort.

How the Test Results Are Used

Results help determine if your theophylline levels are within a safe range. Too little may mean your symptoms aren’t controlled, while too much could lead to side effects like nausea or rapid heartbeat.

Common Side Effects of Theophylline

Theophylline can cause side effects like headaches, nausea, insomnia, or increased heart rate. High levels may also lead to more serious issues, so regular monitoring is important.

Reference range

Therapeutic: 10-20 mcg/mLN/A

Specimen: csf

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.

◆Associated findings1

Short name

Theophylline Level

Frequently asked questions

Why might my doctor ask for this test?
Your doctor may order this test if you’re on theophylline to check if your dose is safe and effective. It’s also used in cases where symptoms persist despite treatment or if you have conditions that affect how your body processes the medication.
What do my test results mean?
Results are compared to a range specific to your age, weight, and health. If levels are too high, your doctor may adjust your dose. If too low, they may increase it. Always discuss results with your provider.
Can I eat or drink before this test?
You can eat and drink normally unless your doctor specifies otherwise. No fasting is required for this blood test.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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