hypovolaemia vs blood disease

hypovolaemia and blood disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
hypovolaemia	Yes	No	No	No
blood disease	Yes	No	No	No

As nouns, blood disease is a hypernym of hypovolaemia; that is, blood disease is a word with a broader meaning than hypovolaemia:

hypovolaemia: a blood disorder consisting of a decrease in the volume of circulating blood
blood disease: a disease or disorder of the blood

Other hypernyms of hypovolaemia include blood disorder.

hypovolaemia (noun)	blood disease (noun)
a blood disorder consisting of a decrease in the volume of circulating blood	a disease or disorder of the blood