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Urea is a metabolic byproduct of amino acid metabolism that is excreted by the kidneys.

Research analysis lead by Kamal Patel
All content reviewed by Examine.com Team. Published:
Last Updated:

Human Effect Matrix

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what supplements affect urea
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
grade-c Citrulline Minor - See study
An increase in urea is seen with citrulline supplementation (possibly due to increased serum ornithine sequestering ammonia)
grade-c Glutamine Minor - See study
An increase in urea has been noted with glutamine supplementation
grade-c Ornithine Minor Moderate See 2 studies
Mixed effects, but it appears that when ammonia is decreased that urea is also increased but if ammonia is unchanged whatever reason for this also means that urea is unchanged.
grade-c Arginine  
grade-c Astaxanthin  
grade-c Chromium  
grade-c Citrullus colocynthis  
grade-c Cocoa Extract  
grade-c Creatine  
grade-d HMB  
grade-d Hibiscus sabdariffa  
grade-d Vitamin C  

All comparative evidence is now gathered in our ​A-to-Z Supplement Reference.

The evidence for each separate supplement is still freely available ​here.