Diabetic Home Care and Monitoring (cont.)
Tests for urinary ketones
Ketone testing is an important part of monitoring in type 1 diabetes, and it is a tool that is often also used in
pregnancies that are complicated by diabetes.
Ketones are formed when the body goes into starvation mode when there is a profound lack of insulin. When the body produces an
insufficient amount of insulin, the cells are unable to
remove glucose from the blood, and the level of glucose in
the blood rises. The cells respond to what appears to be a
lack of glucose by stimulating the body to produce larger
amounts of glucose, and the blood glucose level rises
further. In addition, ketones are produced by the cells.
The presence of ketones signals a condition in diabetics
called ketoacidosis. Ketoacidosis signifies that the cells
are not getting enough glucose.
Severe diabetic
ketoacidosis is a medical emergency since it can result in
loss of consciousness and even death. There is a
correlation between high blood glucose levels and ketones.
The higher the glucose level, the more likely it
is that there are ketones. Therefore, diabetics with blood
glucose levels of 240 mg/dl or greater should test for
urinary ketones. Patients with type 1 diabetes should test for ketones during acute illness and if they are in severe stress. Also, the urine ketones should be checked if any symptoms of ketoacidosis (nausea,
vomiting, abdominal pain) are present.
Ketones can normally be found in the urine. For example, after an overnight fast, ketones can be seen in up to 30% of non–diabetic people. However, these levels of ketone production are usually below the threshold of measurement by the ketone test strips. The strips can also give false positive results when patients are on drugs such as captopril
(Capoten). False negative readings may be seen if the test strips are old, exposed to air, or if the urine is very acidic (such as after drinking a lot of orange juice, which is high in vitamin C).
Tests for ketones are based on the color change that occurs when ketones react with sodium
nitroprusside or similar compounds. The tests are performed in a manner
similar to that of urine glucose testing. There are
different tests for the different types of ketones. For
example, Acetest detects two ketones, acetoacetic acid and
acetone, but does not detect another
ketone, beta–hydroxybutyric acid. Ketostix detects only acetoacetic acid and,
therefore, produces false negative results if only acetone and beta–hydroxybutyric acid are present in the
urine. Ketone tests are supplied as strips or tablets.
The American Diabetes Association advises that ketone testing materials be available in the office setting and that physicians should prefer using blood ketone measurements over urine ketone measurements if possible. Home testing for blood ketones is also available, though not often used.
Next: What additional monitoring does the doctor do? »
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