Blood and water

A lover once said:
Blood was thicker than water.
He proved it.
International normalised ratio
Indicates coagulation.
Radioactive equivalent water thickness
Indicates purity.
But purity of blood
Sometimes
Causes an uproar.
Pure bloods are incorrect.
Still lovers leave.
Blood is thicker than water.
It begs the question then:
When thirst beckons
Why is water chosen?
Drink blood, lover.