Hello and thanks for the query.
Urine varies in appearance, depending principally upon a body's level of hydration, as well as other factors. Normal urine is a transparent solution ranging from colorless to XXXXXXX but is usually a pale yellow. In the urine of a healthy individual the color comes primarily from the presence of urobilin.
Colorless urine indicates over-hydration.
Dark yellow urine is often indicative of dehydration.
Yellowing/light orange may be caused by removal of excess B vitamins from the bloodstream.
Certain medications such as rifampin and phenazopyridine can cause orange urine.
Dark yellow urine also occurs in jaundice but is accompanied by other symptoms of jaundice.
In most likely hood your father in law is passing normal urine and this yellow color is due to the concentrated urine because of summers and B complex vitamins which he might be taking along with his other medications.
I hope to have answered your query however you may revert to me for any other query
Thanks and best of luck.

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