Glucose levels above 11 mmol/L increase the risk of immediate complications, including polyuria, gastroparesis and elevated risk of infection.
High blood glucose levels bind to circulating and endothelial proteins. This is useful as a diagnostic tool, where HbA1c reflects the blood glucose levels over the 3-month lifespan of red blood cells.
However, high blood glucose levels are very damaging to these proteins over a prolonged period, and lead to:
The risk of these complications increases exponentially above an HbA1c of 6.5%.
Conversely, reducing the HbA1c by 1% reduces the risk of microvascular complications by more than one-third. Keeping the HbA1c below 7% reduces the risk of long term vascular complications, but this is improved further by controlling blood pressure and cholesterol.
Consequences of hyperglycemia
While hyperglycemia increases the long-term risk of vascular complications, the immediate symptoms affect your patients’ quality of life right now.
The short-term effects of high glucose levels (above 11 mmol/L) include:
The high glucose levels themselves impair insulin secretion and increase insulin resistance. Therefore, hyperglycaemia worsens and prolongs the hyperglycaemia.
All of these effects of hyperglycemia are improved by reducing glucose levels to 4 – 10 mmol/L.
Stress and sickness
Significant stress and illness raise glucose levels due to insulin resistance caused by elevated cortisol levels as well as sleep deprivation and poor food choices. Hyperglycemia can delay the recovery from illness and emotional stress, so it’s important to have strategies to manage the diabetes during these periods.
These strategies include:
Investigate for underlying infections (See Sepsis) if hyperglycaemia persists.
Increase the insulin doses:
This refers to the period of hyperglycaemic that follows a hypoglycemic event.
The counterregulatory hormones - including noradrenaline, adrenaline, cortisol and glucagon – drive the release of glucose from the liver (hepatic glycogen and gluconeogenesis). This combines with oral glucose treatment to cause immediate hyperglycaemia. These hormones also cause insulin resistance, and this can perpetuate the hyperglycaemia so that it persists for hours afterwards.
The temptation is to treat the patient with more insulin, which can lead to further episodes of hypoglycaemia and rebound hyperglycemia.
The answer is to avoid the hypoglycaemia by reducing the insulin doses rather than chasing down the rebound hyperglycemia that results from it.
Some patients will have a prominent rise in glucose levels first thing in the morning before eating breakfast. It follows the physiological rise in cortisol and growth hormone and is due to insulin resistance at that time of the day.
Managing it can be challenging, but the options include:
Steroids cause insulin resistance and a typical pattern of hyperglycaemia where glucose levels are expected to peak after lunch and dinner and fall to lower glucose levels overnight. While the pattern of hyperglycaemia is the same for the different types of glucocorticoids, the degree of hyperglycaemia is related to the steroid dose. If your patient is on insulin, the dose will need to be titrated according to the dose of steroid.
Managing steroid-induced hyperglycemia will be easier if your patient:
Glucose levels tend to rise in the day or two before menstruation starts or for the first 2 – 3 days of the cycle. This is due to insulin resistance caused by changes in oestrogen and progesterone levels.
These suggestions may help to manage your glucose levels: