One of the main goals of any diabetes control regimen is keeping blood glucose levels in the near-normal range. The cornerstones of most plans to achieve that goal include following a healthy diet, getting regular exercise, and taking insulin or other medicines as necessary.
However, it’s not uncommon for people with diabetes to have other medical conditions that also require taking medicines, and sometimes these drugs can interfere with efforts to control blood glucose. A few medicines, including some commonly prescribed to treat high blood pressure and heart disease, have even been implicated as the cause of some cases of diabetes.
This article lists some of the medicines that can worsen blood glucose control, the reasons they have that effect, the usual magnitude of the blood glucose changes, as well as the pros and cons of using these drugs in people who have diabetes.
Where the problems occur
To understand how various medicines can worsen blood glucose control, it helps to understand how insulin, the hormone responsible for lowering blood glucose, works in the body.
Insulin is released from the beta cells of the pancreas in response to rising levels of glucose in the bloodstream, rising levels of a hormone called GLP-1 (which is released from the intestines in response to glucose), and signals from the nerve connections to the pancreas. The secretion of insulin occurs in two phases: a rapid first phase and a delayed second phase. Both of these phases are dependent on levels of potassium and calcium in the pancreas.
Insulin acts on three major organs: the liver, the muscles, and fat tissue. In the liver, insulin enhances the uptake of glucose and prevents the liver from forming new glucose, which it normally does to maintain fasting glucose levels. In muscle and fat tissue, insulin stimulates the uptake of glucose and prevents the flow of glucose-forming metabolites (products of metabolism) from these tissues to the liver. Insulin does this by interacting with the insulin receptor, a protein that extends from the outside to the inside of liver, muscle, and fat cells.
Once insulin travels from the pancreas via the bloodstream to the target cell, it binds to the receptor on the outside of the cell and starts off signals on the inside of the cell. These signals initiate several of the ultimate actions of insulin, including increasing the number of glucose-transport proteins (proteins that help bring glucose into cells, thereby lowering blood glucose) and increasing the number of enzyme proteins that help break down and use glucose.
The glucose-transport proteins are highly dependent on potassium, and any reduction of potassium in the blood will interfere with the transport of glucose into the cell as well as inhibit insulin secretion in the pancreas, resulting in higher blood glucose. The liver, muscles, and fat tissue are important “sinks” for glucose storage, and anything that interferes with the delivery of glucose to those tissues will tend to raise blood glucose.
As mentioned earlier, the liver can both absorb and produce glucose. Several hormones, as well as drugs, may stimulate the liver’s production of glucose.
Quite a few medicines have been associated with the onset of diabetes or with diminished blood glucose control, but many of them are not commonly used, or the evidence that they raise blood glucose has not been firmly established. However, the following are a few widely used medicines that have been studied extensively and are firmly associated with elevated blood glucose.