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Serum or plasma mass concentration of urea

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

This test measures the amount of urea, a waste product from protein breakdown, in your blood or plasma. It helps assess kidney function and fluid balance.

Quick summary

["Kidney health and fluid balance depend on this test."]

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

Key facts at a glance

LOINC
36798-7
Short code
MRA UE ves-R
Synonyms
MRA UE ves-R
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
20
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
mr-angio
CPT
85651
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

What Does Urea Measure?

Urea is produced when your body breaks down proteins into energy. When kidneys filter waste, they remove urea from your blood. High levels may indicate poor kidney function or dehydration, while low levels could suggest overhydration or liver issues.

Why Might Your Doctor Order This Test?

Your doctor may check urea levels if you have symptoms like swelling, fatigue, or changes in urine output. It’s also used before surgeries, during kidney-related conditions, or to monitor fluid balance.

What to Expect Before the Test

No special preparation is needed. You may fast for 8–12 hours before a blood draw, but always follow your doctor’s instructions. A nurse will insert a needle into your arm to collect a blood sample.

What Happens During the Test?

A small amount of blood is drawn from your arm and sent to a lab. The lab uses a specialized method (like enzymatic analysis) to measure urea concentration in your serum or plasma.

Reference range

Adult males: 0-15 mm/hr; Females: 0-20 mm/hrN/A

Specimen: serum

No special preparation required. CRP may be affected by acute illness.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urea Level

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–2 business days, depending on your lab’s processing time. Your doctor will share them with you during your follow-up visit.
Can I eat or drink before this test?
Most labs recommend fasting for 8–12 hours before a blood draw for urea testing. Check with your doctor or lab for specific instructions, as some may allow water.
What are common causes of high urea levels?
High urea levels can result from kidney disease, dehydration, high protein diets, heart failure, or certain medications. If you notice symptoms like swelling or fatigue, talk to your doctor.
  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