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Serum or Plasma Creatinine Concentration (Mass Concentration)

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

This test measures the amount of creatinine, a waste product from muscle metabolism, in your blood. It helps assess how well your kidneys are filtering blood.

Quick summary

["Kidney function check via creatinine levels—simple but critical for long-term health."]

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

Key facts at a glance

LOINC
36042-0
Short code
XR tomo Knee-L
Synonyms
XR tomo Knee-L
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr-tomography
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 Your Kidneys Matter

Creatinine is a byproduct of muscle breakdown that your kidneys filter out of your blood. When kidneys don’t work well, creatinine builds up, which can signal kidney damage or disease. This test is one of the most common ways doctors monitor kidney health.

How the Test Works

A small blood sample is taken from your arm. The lab uses a method like enzymatic or chemiluminescent immunoassay to measure creatinine levels. Results help determine if your kidneys are functioning normally or if further evaluation is needed.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to avoid certain medications or foods for a short time if instructed by your doctor. Drink plenty of water the day before if your doctor recommends it, as hydration can affect results.

Possible Results and Next Steps

Your results will be compared to a reference range, though exact values can vary by lab. High levels may indicate kidney problems, while low levels could suggest dehydration or muscle loss. Your doctor will discuss what your results mean in your specific situation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

What causes high creatinine levels?
High creatinine levels can result from kidney disease, dehydration, heart failure, severe muscle breakdown (e.g., from injury or illness), or certain medications. If you have a history of these conditions, your doctor may monitor your levels more closely.
What causes low creatinine levels?
Low creatinine levels may occur if you’re dehydrated, have very little muscle mass, or are taking certain medications that affect kidney function. In rare cases, it could also signal an underlying metabolic issue, so follow-up with your doctor is important.
Can diet affect creatinine levels?
Diet alone doesn’t change creatinine levels, but hydration status does. Drinking enough water helps your kidneys filter waste properly. If you’re unsure about your diet, ask your doctor or dietitian for personalized advice.
  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