Diabetes Insipidus Lab Values Explained

Only a laboratory testing is able to confirm the presence of diabetes insipidus. These tests in some form have been available in the United States since the 1930s. If the clinical presentation of this condition is suggested by the signs and symptoms being suffered, then a medical provider will order a 24 hour urine collection to determine how much volume is being passed through the body.

There are also certain measurements that are typically performed at the laboratory as the volume of urine is being considered. This includes glucose levels, serum electrolytes, urinary specific gravity, ADH levels, and plasma/urinary osmolality.

Testing is most accurate when the patient can be as dehydrated as the can tolerate. This will allow the anti-diuretic hormone ADH to be at its highest concentrated levels for the testing period. Even water deprivation may be considered as part of the testing process if it can be safely performed and the diagnosis is uncertain.

Once the 24 hour urine collection period has been evaluated, the laboratory will come back with results that are communicated through the medical provider. Here are those diabetes insipidus lab values explained.

What Do the Diabetes Insipidus Lab Values Mean?

There are two hallmarks that will confirm the presence of diabetes insipidus. The first is the measurement of specific gravity. If the urine has a specific gravity of 1,005 or less, then this can indicate the presence of this health condition. Urinary osmolality that is less than 200 mOsm/kg is also a strong indicator of the presence of diabetes insipidus. The average plasma osmolality on a random patient test is 287 mOsm/kg of water.

If there are large volumes of urine that is very dilute or clear, then this can be a visual indicator that these testing values may be present.

When these lab values are present, combined with high daily urine output, then desmopressin or vasopressin may be administered to confirm the diagnosis that the lab has discovered. If the specific gravity values and urinary osmolality normalize after the synthetic hormone has been administered, then this will confirm the diagnosis.

For certain patients, a blood test may be ordered as part of the diabetes insipidus process. The goal is to measure the amount of sodium that is in the blood. If sodium levels are high, especially when combined with a water deprivation test, then this can indicate the presence of diabetes insipidus.

A patient’s body weight may also be tested during the 24 hour urinary collection period if water deprivation is being used as a testing factor. In this circumstance, if a patient loses more than 5% of their body weight in 12 hours or less, sees a decline in blood pressure, or an increase in heart rate, then this may also confirm the diagnosis. The specific values which would then trigger a desmopressin or vasopressin injection are often determined by the medical provider.

If these physical changes take place, but the hormone treatment does not stop the bothersome signs and symptoms mentioned, then the diagnosis is nephrogenic diabetes insipidus.

The Importance of Discovering the Right Type of Diabetes Insipidus

Nephrogenic diabetes insipidus occurs because the kidneys are not responding to an appropriate level of ADH in the body. This means they continue to excrete large amounts of urine that is very dilute. It is more uncommon than central diabetes insipidus, which occurs because of a failure in the pituitary gland to secrete the necessary hormone.

Treating central diabetes insipidus based on the lab values present often involves taking hormone injections, nasal sprays, or certain medications that can stimulate the pituitary gland to start making ADH once again. In nephrogenic diabetes insipidus, the goal is to prevent dehydration by increasing water intake while reducing salt and protein in the diet. Some patients may be encouraged to take NSAIDs or thiazide diuretic to decrease the amount of urine that is excreted from the body.

What Is the Prognosis of Diabetes Insipidus Lab Values?

With treatment, the prognosis for people diagnosed with either type of diabetes insipidus is good. The goal is to get a patient the diagnosis they need through testing before there is a severe episode of dehydration. Even children diagnosed with this condition can develop normally, though nephrogenic diabetes requires immediate identification and treatment to maintain a good prognosis.

Assuming the condition hasn’t been genetically inherited, the correction of the lab values discovered through testing will usually help kidney function begin returning to normal.

Anyone who suspects that they may have diabetes insipidus should contact their local medical provider for testing so that lab values can be established. Make the appointment if necessary, discussion the information here with your doctor, and then begin to develop the treatment plan you may need to restore your health.