Urea

A product of amino acid breakdown which is excreted in urine.
Reflects glomerular filtration with mild increases often
reflecting hypovolaemia and higher values indicating renal
insufficiency. Always worth interpreting alongside creatinine,
with the latter acting as a better indicator of renal function.
Some normal horses (especially cold-blooded types) may have
slightly higher values, alongside creatinine concentrations well
within reference intervals.

See also
Creatinine
Polydipsia and polyuria