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Serum or Plasma Mass Concentration of Methotrexate (MTX)

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

This test measures the amount of methotrexate, a medication used to treat certain cancers and autoimmune conditions, in your blood.

Quick summary

["Knowing your MTX levels helps doctors monitor your treatment and prevent side effects."]

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

Key facts at a glance

LOINC
98990-5
Short code
MTX 18h p SerPl-sCnc
Synonyms
MTX 18h p SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 doctor may order this test if you’re taking methotrexate to check how much of the drug is in your blood. This helps ensure the dose is safe and effective for your condition.

What to Expect Before the Test

You’ll typically have a small needle inserted into your arm or hand to draw blood. It usually takes a few minutes, and you may feel a brief pinch. No special preparation is needed unless instructed otherwise.

What the Results Mean

Results show the amount of methotrexate in your blood, measured in micrograms per milliliter (mcg/mL). Lower levels may indicate the drug isn’t working as expected, while very high levels could signal toxicity.

Common Conditions Monitored

This test is often used to monitor patients with rheumatoid arthritis, psoriasis, or certain types of cancer (e.g., leukemia, lymphoma) treated with methotrexate to avoid overdose or underdose.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

MTX Level

Frequently asked questions

How often should I get this test?
Your doctor will determine the timing based on your treatment plan. It’s usually done weekly or monthly, depending on your medication schedule and health status.
What happens if my MTX levels are too high?
If levels are dangerously high, your doctor may adjust your dose, increase fluids, or give you medications to help your body process the drug more quickly. They’ll work with you to bring it back to a safe range.
Can I eat or drink before this test?
You can eat and drink normally unless your doctor specifies otherwise. Some tests require fasting, but this one does not.
  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