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Drug Concentration Monitoring (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of certain medications in your blood to ensure they are at safe and effective levels.

Quick summary

Your doctor may order this test to prevent harmful side effects or ensure proper treatment.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
28160-0
Short code
MEDICATIONSARETAKINGOVERMYLIFE
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
reported-living-hiv
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

Doctors perform drug concentration tests when medications are used at high doses, for long-term treatment, or when side effects are a concern. It helps adjust doses to avoid toxicity or ineffectiveness.

How the Test Works

A blood sample is taken and analyzed using sensitive techniques like immunoassay or chromatography to detect and quantify specific drugs in your bloodstream.

Common Medications Monitored

This test can check levels of many drugs, including antibiotics, antidepressants, antiepileptics, chemotherapy agents, and others. Your doctor will specify which medication(s) are being monitored.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours if your doctor specifies a fasting sample. Wear comfortable clothing for the blood draw.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormally high drug levels may cause toxicity (e.g., dizziness, kidney damage, or heart rhythm issues), while low levels may mean the medication isn’t working as intended. Regular monitoring helps balance safety and effectiveness.

Short name

Drug Levels

Frequently asked questions

How often will I need this test?
Your doctor will determine the timing based on your medication, condition, and response. Some tests may be done weekly, monthly, or as needed for adjustments.
What happens if my drug levels are too high or too low?
If levels are too high, your doctor may reduce the dose or change the medication. If levels are too low, they may increase the dose or check for interactions with other drugs.
Can I eat or drink before this test?
Follow your doctor’s instructions—some tests require fasting, while others allow water or light snacks. Always confirm with your healthcare provider.
  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 16, 2026. · Read our editorial policy