Levothyroxine Absorption Panel, Serum/Plasma
This panel measures how well your body absorbs levothyroxine, a thyroid hormone medicine, by checking hormone levels in blood at set times after a dose.
["It helps your care team understand whether your thyroid medicine is being absorbed properly or if absorption problems may explain poor response."]
Key facts at a glance
- LOINC
- 90795-6
- Short code
- Levothyroxine absorption pnl SerPl
- Synonyms
- Levothyroxine absorption pnl SerPl
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85610
- SNOMED
- 396252006
- 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
What This Panel Measures
The panel typically checks thyroid hormone levels in serum or plasma before and at intervals after a dose of levothyroxine. It may include thyroid stimulating hormone (TSH) and free thyroxine (free T4), which help show how much hormone is circulating and how your body is responding.
Why Your Clinician Might Order It
Your clinician may order this panel if your thyroid hormone levels stay low or your symptoms do not improve despite taking levothyroxine. It can also be considered when there is concern about absorption problems in the stomach or intestines.
How the Test Is Done
Blood samples are usually collected at scheduled times around a levothyroxine dose. The exact timing and number of samples are set by the ordering laboratory or clinician, so follow their instructions carefully, including whether to take the medicine at home beforehand.
What the Results Mean
Results are interpreted as a pattern over time rather than as a single number. A rise in thyroid hormone levels after the dose suggests absorption is occurring. Your clinician will compare results with your dose, other medicines, and health history to decide if changes are needed.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Take your thyroid medication after the blood draw if applicable. No fasting required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Levothyroxine Absorption Test Panel
Frequently asked questions
Do I need to fast or stop my thyroid medicine before this test?
Can other medicines or supplements affect the results?
Is one blood draw enough for this panel?
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 16, 2026. · Read our editorial policy