A diagnosis of dehydration is frequently based upon clinical signs and symptoms, and appropriate treatment is given. Laboratory testing is typically not required for mild to moderate dehydration, but a variety of non-laboratory evaluations may be used to assess an individual with more serious symptoms.
These may include an evaluation of:
- Urine output and production of tears
- Examination of dryness of skin and mucous membranes
- Breathing rate – is it rapid?
- Heart rate – is it rapid?
- Blood pressure – is it low?
- Skin turgor – when a fold of skin is pinched and then released, does it bounce back in shape or only slowly relax?
- Capillary refill rate – is it slower than normal?
- Do eyes appear sunken and, if so, to what degree?
- State of consciousness
In cases of severe dehydration, laboratory testing is frequently ordered to identify electrolyte and acid-base imbalances, to evaluate kidney function, and general health status. If imbalances and/or organ dysfunction are found, then serial testing may be performed to monitor the person over time and their response to treatment. Testing may include:
- Basic Metabolic Panels (BMP) – these panels of tests can give the doctor information on general health as well as acid-base balance and kidney function:
- Urinalysis – both to evaluate how much urine is being produced and to examine its color and concentration
- CBC – to evaluate blood cells and the balance between the solid and liquid portions of the blood; specifically, one component, the hematocrit, can be elevated with dehydration.
- Glucose – to detect a high level that may indicate uncontrolled diabetes
- Urine and/or blood osmolality – evaluates the body's water balance
If the cause of dehydration is apparent, then usually no other testing is necessary. However, a variety of tests may be performed when the cause is unknown, to diagnose and address underlying conditions, such as those associated with prolonged diarrhea and/or vomiting.
- Stool Culture – to look for bacterial infection as a cause for diarrhea
- Clostridium difficile and C. diff toxin test
- O&P – to detect intestinal parasites
A wide variety of other tests may be done depending on what is suspected to be the underlying cause of the signs and symptoms, such as: