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Serum or Plasma Mass Concentration of Nitrogenous Waste Metabolites (e.g., creatinine, urea, or other small organic compounds)

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

This test measures levels of certain waste products in your blood that form during normal metabolism. It helps assess kidney function and overall fluid balance.

Quick summary

["Kidney health and fluid balance monitoring"]

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

Key facts at a glance

LOINC
56294-2
Short code
Johnson grass IgG4-mCnc
Synonyms
Johnson grass IgG4-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 doctor may order this test if you have symptoms like swelling, fatigue, or frequent urination, or if they suspect kidney problems. It can also be part of routine check-ups or before certain treatments.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab uses a specific method. Bring your test list and any medications.

What Happens During the Test

A healthcare provider will collect a blood sample from a vein in your arm. You may feel a slight pinch, but it usually takes just a few minutes. The sample is sent to the lab for analysis.

What the Results Mean

Higher-than-normal levels may signal kidney issues, dehydration, or other metabolic conditions. Lower-than-normal levels could indicate overhydration or liver/kidney problems. Your doctor will interpret results in the context of your health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Nitrogenous waste screening

Frequently asked questions

What does a ‘mass concentration’ test measure?
It quantifies the total amount of certain waste compounds (like nitrogenous byproducts) in your blood, often used to assess kidney function or fluid balance.
Can I eat or drink before this test?
Check with your lab or doctor—some tests require fasting, while others don’t. Follow their instructions to ensure accurate results.
Is this test painful?
The blood draw itself is quick and mild discomfort. Most people feel fine afterward. If you’re anxious, ask your provider about numbing cream or other options.
  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