3 Monitoring ketone levels
Ketones, which are formed when fats in the body are broken down, are an alternative energy source, and are usually only present when there is insufficient glucose to meet the body's energy requirements. They can occur in small quantities in someone without diabetes, after prolonged fasting. The presence of insulin, however, normally suppresses the production of significant amounts of ketones. In people with Type 1 diabetes who are deficient in insulin (perhaps because they have forgotten to take their insulin injections, for example), ketones can be produced in large amounts because, although there is plenty of glucose available in the blood, the body is unable to use it for energy without insulin. Ketones accumulate in the blood, altering the acidity (the pH level). They are removed from the body in the urine and via the lungs in the breath. They have a distinctive ‘pear-drop’ smell or nail varnish type odour, which you may notice on someone's breath when you are close to them.
In people with diabetes, ketones are a sign of very poor diabetes control. If ketones build up in sufficient quantities in the blood, the condition of diabetic ketoacidosis (DKA) develops , which is a medical emergency. Testing for ketones when the blood glucose is high, especially if the person with diabetes is unwell, is essential to identify DKA, or to prevent it developing further, by treatment with fluids and insulin.
Ketones can be detected in the urine by using a reagent strip (Figure 9). Usually the testing strip consists of a white plastic strip with a coloured pad stuck to it. The pad for ketones may be one of several pads for various tests if the urine is being tested at the GP surgery or hospital clinic. The pad is dipped briefly into a specimen of urine, and then examined after the recommended time (usually about 30 seconds) for a change in colour. The intensity of the colour change depends on the amount of ketones in the urine. No colour change means there are no ketones in the urine, and is said to be a negative result. A very strong colour change means that ketones are present in high quantities, and treatment to prevent DKA is required urgently.
People with Type 1 diabetes can obtain ketone testing strips on prescription from their GPs. It is useful to have a supply available to test for ketones during periods of illness, when people may be more likely to develop DKA. By frequently testing the blood glucose and ketones, the person may be able to make decisions about adjustments to their insulin dose to avoid hospitalisation with DKA, or at least recognise that they need to contact a health care professional for advice.
The presence of ketones in the blood is usually tested in a hospital laboratory. However, at the time of writing (2005), one blood glucose meter on the market has the facility for home testing of blood ketones using specific strips. However, most people use urine testing to detect ketones.