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Methotrexate (MTX) Serum Concentration

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

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

Quick summary

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

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

Key facts at a glance

LOINC
4324-0
Short code
MTX Dose
Synonyms
MTX Dose
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 Matters

Methotrexate works by slowing the growth of cancer cells and reducing inflammation in conditions like lupus or psoriasis. However, high levels can cause nausea, mouth sores, or long-term damage to organs like the liver or kidneys. Regular monitoring ensures your dose stays safe and effective.

When You Might Need It

Your doctor may order this test if you’re taking methotrexate for cancer treatment, rheumatoid arthritis, or another condition. It’s often checked before starting treatment, during ongoing therapy, or if you experience side effects.

How the Test Works

A blood sample is taken from a vein in your arm. The lab uses a sensitive test (likely immunoassay or chemiluminescence) to measure methotrexate levels in your serum, which is the liquid part of blood after clotting.

What the Results Mean

Results are usually reported in nanograms per milliliter (ng/mL) or micrograms per liter (µg/L). Your doctor will interpret these numbers based on your specific treatment plan, medical history, and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

MTX Level

Frequently asked questions

What could cause abnormal results?
Low levels may mean your medication isn’t working as intended or you’re not taking it correctly. High levels can indicate toxicity, especially if you’ve missed doses, had nausea/vomiting (which may reduce absorption), or had a fever (which can increase metabolism).
How often should I get this test?
Your doctor will determine the timing based on your treatment schedule. For example, if you take weekly doses, you might get tested before or after your dose. Follow-up tests may be needed if you’re experiencing side effects or adjusting your medication.
Can I eat or drink before the test?
Typically, you can eat and drink normally unless your doctor instructs otherwise. Some medications (like folic acid supplements) may affect MTX levels, so check with your provider if you’re taking any.
  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