Serum osmolality is a measurement of chemicals that are in the liquid part, or the serum, of a person’s blood. Unlike other tests for diabetes insipidus that focus on the urine, this test requires that a blood sample be taken. Once collected, it will be taken to a laboratory so that the amount of chemicals can be determined. In most situations, the diabetes insipidus serum osmolality test takes about 4 hours to produce results.
It is important to note that values which are considered to be “normal” will vary from laboratory to laboratory. A medical provider will interpret the results that have been found from the serum osmolality test and other health factors which may be affecting results to determine if diabetes insipidus is a potential diagnosis.
Why Is the Serum Osmolality Test Requested?
The main reason why a medical provider will order a serum osmolality test is the check the balance of chemicals and water in your blood. This helps to determine if there is a severe level of dehydration or overhydration that may need to be treated.
The diabetes insipidus serum osmolality test will also check to make sure the body is producing enough of a hormone called ADH. This regulates how much urine the kidneys will eventually excrete.
Some patients may also be experiencing seizures because of an imbalance of electrolytes and this testing protocol can help to determine if this has happened. Exposure to certain poisons can also be confirmed with a serum osmolality test.
How To Prepare for the Serum Osmolality Test
There are some medications that may affect the results of a diabetes insipidus osmolality test. Anyone who is considering this blood test should inform their medical provider of all medications, vitamins, and supplements that are being taken. This can help the laboratory be able to correctly interpret the results that they see.
Some patients may also wish to speak with their medical provider about their concerns regarding the need for this test or what the results may mean. This guide reports only average values based on all testing. Your specific test results may not fit into a normal range, but may still be considered normal for you.
What Are the Average Values for Serum Osmolality?
In a healthy individual, normal serum osmolality values are typically between 278-300 milliosmoles per kilogram of water [mOsm/kg]. These results may be slightly higher or lower depending on the laboratory.
If the serum osmolality values are high, then the most common cause is dehydration. This means there isn’t enough water in the blood supply compared to what should be there. It can also be commonly caused by high levels of salt or glucose in the blood, which is seen when diabetes mellitus is present and poorly controlled.
People who have suffered some form of damage to the kidneys may also see high serum osmolality values with this blood test. This may cause a build-up of urea in the blood, which affects the laboratory results. Certain poisons can also cause high results, such as rubbing alcohol, ethanol, methanol, and antifreeze.
All of these factors must be considered before diabetes insipidus will be the diagnosis, as it will also cause high values for this blood test.
If the serum osmolality values are lower than the normal range, then this indicates that there is too much water in the body. It may also mean that sodium levels are too low, which is often caused by certain medications that control blood pressure. Certain diseases which cause an overproduction of ADH can also cause low results.’
What Affects the Serum Osmolality Test?
If your medical provider is recommending that you take a diabetes insipidus serum osmolality blood test, then be sure to inform them if you have recently consumed alcoholic beverages. When consumed right before the test, then the results discovered by the laboratory may not be helpful. This test is also not considered suitable for patients who have recently had a blood transfusion.
What To Think About with the Diabetes Insipidus Serum Osmolality Test
This blood test is often ordered with a diabetes insipidus urine osmolality test so that the two results can be compared. The measurements help medical providers be able to determine kidney functionality so that the imbalance of electrolytes and water within the body can be investigated.
There are times when the amount of ADH in the body will increase even though all other osmolality tests come back as being normal. It is up to your medical provider to determine if this condition requires further testing.