Why get tested?
To help evaluate the body’s water and electrolyte balance and to help investigate hyponatremia and increased or decreased urine production; to detect the ingestion of certain toxins (such as methanol); to monitor the effectiveness of treatment for conditions affecting osmolality; to help determine the cause of chronic diarrhea

When to get tested?
When a patient has a low sodium level; when a patient is taking mannitol; when a doctor suspects that a patient may have ingested a toxin such as methanol or ethylene glycol; when a patient is producing significantly increased or decreased amounts of urine; when a patient has chronic diarrhea

Sample required?
A blood sample drawn from a vein in your arm and/or a random urine sample; sometimes a fresh, liquid stool sample