Platform
Company
Drug Monitoring
Review status
Currently under review
Pending specialist review and validation.
The theophylline test measures the amount of theophylline circulating in your blood. Theophylline is a bronchodilator medicine used to help relax the muscles around the airways in conditions such as asthma and chronic obstructive pulmonary disease. Because the body processes this drug in complex ways and small changes in dose can matter, blood level monitoring is often used to guide safe treatment.
Your sample is taken from a vein. For the most useful result, the timing of the blood draw in relation to your last dose is important, often just before the next scheduled dose. Your clinician may check levels after starting therapy, after a dose change, or when there are symptoms that could be related to the medicine.
Knowing your theophylline level helps balance effectiveness with safety. If the amount in your blood is too low, your breathing symptoms may not be well controlled. If it is too high, you may be more likely to have side effects such as nausea, headaches, tremor, or a racing heartbeat. Monitoring is especially useful when other illnesses, new medications, or lifestyle changes could alter how your body handles the drug.
This test is commonly ordered after dose adjustments, when symptoms persist, when side effects appear, or when you start or stop medicines that interact with theophylline. People with liver problems, heart failure, fever, or older adults may process the drug differently, so closer monitoring can be needed.
Your clinician will interpret your result alongside why the test was ordered, when the blood was drawn relative to your last dose, and how you are feeling. A result interpreted as higher than the target for you may suggest a greater risk of side effects, and your clinician may adjust the dose, change the schedule, or look for interactions. A result interpreted as lower than the target may mean the medicine is not likely to control symptoms, and your dose or timing might be adjusted.
If results are unexpected, your care team may confirm the timing of the test, review all medications and supplements, check liver or kidney function, or repeat the level. Do not change your dose or stop the medicine on your own. Seek medical help promptly if you develop worrisome symptoms such as persistent vomiting, marked restlessness, or an irregular heartbeat.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Levels are most informative when the sample is collected at a consistent time in your dosing cycle, often just before the next dose. Off‑schedule draws can mislead interpretation.
Tobacco smoke and some cannabis products can increase how quickly your body clears theophylline, lowering levels; stopping smoking can have the opposite effect.
Certain antibiotics, antifungals, antidepressants, and heart or seizure medicines can raise or lower theophylline levels. Examples include ciprofloxacin, erythromycin, rifampin, phenytoin, and carbamazepine.
Liver disease, heart failure, fever, and older age can reduce clearance, increasing levels. Children may clear theophylIine differently, requiring individualized monitoring.
Viral illnesses and sustained fever can slow theophylline metabolism, raising blood levels even if your dose has not changed.
Caffeine is in the same drug family and may add to side effects. Major diet shifts, such as high‑protein or very low‑carbohydrate diets, can alter metabolism.
Switching between immediate‑release and extended‑release products or between brands can change absorption. Missed or extra doses directly affect measured levels.
Body changes in pregnancy can alter drug handling. Levels should be interpreted with clinical context and may need closer follow‑up.
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