Urine specific gravity measures the concentration of dissolved solutes in urine relative to water. It reflects the kidney's ability to concentrate or dilute urine in response to hydration needs. Normal SG ranges from 1.002 to 1.030.
Fixed SG of 1.010 (isosthenuria) indicates impaired kidney concentrating ability. Persistently dilute urine (below 1.003) can indicate diabetes insipidus. Very high SG reflects dehydration or SIADH.
FAQs
What does fixed SG 1.010 mean?
Isosthenuria means the kidney cannot concentrate or dilute urine, reflecting severe tubular dysfunction in CKD. The filtrate is essentially unmodified.
What is diabetes insipidus?
Caused by ADH deficiency (central) or kidney resistance to ADH (nephrogenic). Produces large volumes of dilute urine with extreme thirst. SG is typically below 1.003.
Does high SG always mean dehydration?
Not always. SIADH, high protein diet, and contrast agents can raise SG. Dehydration is the most common cause.
Can colour and SG indicate hydration?
Yes. Pale urine with SG below 1.010 indicates good hydration; dark amber urine with SG above 1.020 indicates dehydration.
