While insulin treatment can be a near-daily task for many nurses in many different roles, we’ve found that one of the most common incorrect answers on our Pharmacology Exam deals with insulin requirements for aging patients.
That question reads: “True or False: Your patient’s need for insulin will increase as your patient ages”.
Most taking the exam tend to quickly arrive at a response of “True”, adhering to the common assumption that as we age, we simply need more of almost everything to keep ourselves going. However, in this case that assumption does not hold up under scrutiny. When thought is given to the underlying pharmacology of how the body uses insulin and the role kidneys play in the regulation of blood glucose, you should arrive at a different conclusion.
Insulin is a blood glucose lowering hormone. The glucose itself ultimately has to get into a cell in order for the body to metabolize it for energy. Therefore, when glucose enters the cell, it is no longer in the bloodstream, and as such, the blood glucose reading will go down. The kidneys play a role in this process.
Under normal circumstances, the glucose remaining in the blood after the cells have absorbed what they need is completely reabsorbed into the bloodstream by the tubules in the kidneys. In these circumstances, there will be no sugar present in urine.
In turn, the insulin itself is also ultimately metabolized/neutralized in the kidneys.
With age, we simply have fewer and fewer functioning nephrons, and therefore, less kidney function. It is estimated that at age 50, an average person has only about 50% of their nephrons left functioning.
So, let’s re-examine our original question of whether or not your patient’s need for insulin will increase as your patient ages…
Since your kidneys do not function as optimally as you age, they can’t metabolize the insulin as well. That means the insulin stays in the bloodstream longer in older patients. As a result, the older you get, the less insulin you need to be given because it stays available to the cells longer than in younger people. Simply put, decreased kidney function comes with the adverse benefit of less frequent insulin needs! So the correct answer to the question “True or False: Your patient’s need for insulin will increase as your patient ages” – is FALSE!