What are they used for?
Osmolality tests may be used for a variety of reasons. A blood osmolality test, also known as a serum osmolality test, is most often used to:
Check the balance between water and certain chemicals in the blood.
Find out if you have swallowed a poison such as antifreeze or rubbing alcohol
Help diagnose dehydration, a condition in which your body loses too much fluid
Help diagnose overhydration, a condition in which your body retains too much fluid
Help diagnose diabetes insipidus, a condition that affects the kidneys and can lead to dehydration
Sometimes blood plasma is also tested for osmolality. Serum and plasma are both parts of the blood. Plasma contains substances including blood cells and certain proteins. Serum is a clear fluid that does not contain these substances.
A urine osmolality test is often used along with a serum osmolality test to check the body's fluid balance. The urine test may also be used to find out the reason for increased or decreased urination.
A stool osmolality test is most often used to find out the reason for chronic diarrhea that is not caused by a bacterial or parasitic infection.
