Osmolality Urine Test

What is the purpose of this test?

Osmolality testing measures the concentration of certain dissolved particles in a fluid (blood, urine, or stool). These particles may include glucose (sugar), urea (a byproduct of the liver), and electrolytes, such as sodium, potassium, and chloride. Electrolytes are particles with electrical charges that break down into ions once dissolved in water or body fluid. As a result, electrolytes also help regulate the body's fluid levels. The Osmolality Urine Test measures the amount of toxins in a urine sample to help assess the body's water and electrolyte balance. 

What conditions may cause elevated osmolality levels?

Many different conditions can cause elevated osmolality levels or an unhealthy fluid balance. These include excess salt intake, kidney disease, heart disease, and poisoning. In addition, this test may assist in diagnosing and monitoring the following conditions:

• Check the body's water balance and urine concentration
• Determine if an individual has been poisoned with toxins such as antifreeze or rubbing alcohol (methanol or ethylene glycol)
• Dehydration (the loss of too much body fluid)
• Overhydration (the retention of too much body fluid)
• Diabetes insipidus, a condition that affects the kidneys and can lead to dehydration

When should I order an Osmolality Urine Test?

This Osmolality Urine Test can be ordered if an individual is suspected of having ingested a toxin such as antifreeze or rubbing alcohol (methanol or ethylene glycol).

Additionally, individuals may order this test if they have unexplained low blood sodium levels (hyponatremia) or signs and symptoms that a healthcare provider suspects may be due to low blood sodium, such as:

• Excessive thirst
• Confusion
• Nausea
• Headache
• Lethargy
• In severe cases, seizures or coma

This Osmolality Urine Test may also be ordered along with an Osmolality Blood Test when a health provider wants to compare urine results with the serum osmolality or when the individual being tested is producing increased or decreased amounts of urine.