In the short term, consistent high blood glucose levels can lead to a condition called diabetic ketoacidosis (DKA).
Why does this happen?
This happens because of a lack of glucose entering the cells where it can be used as energy. The body begins to use stores of fat as an alternative source of energy, and this in turn produces an acidic by-product known as ketones.
How ketones affect the body
Ketones are very harmful and the body will immediately try to get rid of them by excreting them in urine. Consequently, when ketones are present and blood glucose levels are rising, people often become increasingly thirsty as the body tries to flush them out.
If the level of ketones in the body continues to rise, ketoacidosis develops (ketoacidosis means acidity of the blood, due to an excess of ketones in the body). Their harmful effect becomes more apparent, and nausea or vomiting may start. In addition, the skin may become dry, eyesight blurred and breathing deep and rapid.
Unfortunately, because of vomiting, the body becomes even more dehydrated and less efficient at flushing out the ketones, allowing levels to rise even faster. As the level of ketones rise, it may be possible to smell them on the breath – often described as smelling like pear drops or nail varnish.
Eventually, if untreated, the level of ketones will continue to rise and, combined with high blood glucose levels, a coma will develop which can be fatal. However, at any of these intermediate stages, ketoacidosis can be treated and damage usually limited. Obviously, the sooner, the better.
Who is at risk?
Any person with diabetes who relies on administering insulin (ie by injections or an insulin pump) could develop diabetic ketoacidosis. In exceptionally rare cases people controlling their diabetes with diet or tablets have been known to develop ketoacidosis when severely ill.
During illness
The high-risk time for developing ketoacidosis is when a person is unwell, as part of the body's response to illness and infection is to release more glucose into the bloodstream, and to stop insulin from working properly. This happens even if the person loses their appetite or goes off food altogether.
During periods of illness, even if you are not eating, insulin is still needed and it is important never to stop taking your insulin. You should do more frequent blood glucose testing. We recommend that you test at least four times a day during periods of illness. Ask your care team for help if you are worried.
Detecting ketones
Ketones are easily detected by a simple urine test, using strips available on prescription. People with diabetes should test their urine for ketones if their blood glucose is high (usually over 15mmol/l) or if they have any symptoms of ketoacidosis.
If someone discovers high levels of ketones in their urine (the test strips will tell you if levels are high), and especially if their blood glucose levels are high, they should call their doctor or diabetes specialist nurse immediately, or go to their nearest casualty department.