Valacyclovir (Pharmacokinetic Profile) – Serum Concentration
This test measures the amount of valacyclovir, an antiviral medication, in your blood serum to assess how your body is processing the drug.
["This helps doctors check if your dose is working properly and adjust it if needed."]
Key facts at a glance
- LOINC
- 73097-8
- Short code
- valACYclovir ind plt IgM SerPl Ql FC
- Synonyms
- valACYclovir ind plt IgM SerPl Ql FC
- Category
- hematology
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- flow-cytometry
- CPT
- 82784
- 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 Is Done
Your healthcare provider may order this test if you’re taking valacyclovir (Valtrex) for conditions like cold sores, genital herpes, or shingles. It may also be used to monitor treatment response or detect drug levels in unusual circumstances, such as kidney issues or high doses.
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 takes about 5 minutes, and you may feel a brief pinch. If you’re on blood thinners or have a history of clotting, let your doctor know.
What the Test Results Mean
Results are typically reported as the concentration of valacyclovir in your blood (measured in micrograms per milliliter). While reference ranges vary by lab, higher-than-expected levels may indicate improper metabolism or dosing issues, while very low levels could suggest insufficient medication absorption.
Common Reasons for Testing
Doctors may order this test to verify whether your valacyclovir dose is therapeutic (effective) or if adjustments are needed. It’s also used in research or clinical trials to study drug pharmacokinetics.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Valacyclovir levels help ensure safe and effective antiviral therapy. Abnormal results may prompt dose changes, especially in patients with kidney problems (valacyclovir is metabolized by the kidneys) or those taking medications that interact with it. Low levels could indicate poor absorption, while high levels may signal toxicity or dosing errors.
Short name
Valacyclovir Levels
Frequently asked questions
How long does it take to get my valacyclovir blood test results?
Can I eat or drink before this test?
Is there any risk of side effects from the blood draw?
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