When do blood glucose levels start to impact K?

This is part two of a question that was emailed to me. The questions were about how different factors impact the movement of potassium inside the body.

In my hyperkalemia assessment form, I highlight that hyperglycemia can lead to hyperkalemia. In these cases, the primary treatment goal is to bring the glucose levels down. But how high does it need to go before you see the shift? Let’s dig in.

Why are blood glucose levels (BG) and potassium (K) related?

People with diabetes are more likely have changes in their blood glucose levels. According to this excellent article on Hyperkalemia in Diabetes Mellitus Setting, there are at least three mechanisms that increase the risk of hyperkalemia for those living with diabetes:

1. Impaired potassium excretion
2. Impaired renal tubular function
3. Reduced ability to shift potassium into the cells

What role does insulin play in potassium homeostasis?

Insulin increases the entry to potassium into the cells. This is a similar job to how insulin increases the entry to glucose into the cells. In fact, increases in serum potassium levels stimulates insulin production from beta-cells independently of glucose.

I use a hallway and clinic rooms analogy to describe this action to patients. I will say, that our blood stream is like a hallway. Our clinic rooms are the cells. To have an appointment, we need to get people out of the hallways and into the clinic rooms. Insulin is what opens the doors to the clinic rooms. Without insulin, people can’t get inside. Just like, how the glucose or the potassium can get stuck in the wrong place without insulin.

Does insulin resistance (as seen in T2DM) lead to reduced potassium uptake?

Insulin resistance describes a scenario where insulin is present but the cells in the body aren’t responding to it. In this way, hyperglycemia can occur despite normal insulin levels. So if this happening for the glucose, does it happen to the potassium too?

The authors of our article explicitly state that it doesn’t. Potassium uptake is preserved even in states of insulin resistance.

How does hyperglycemia impact potassium levels?

In addition to hormonal changes (specifically related to insulin and aldosterone), hyperglycemia itself can contribute to hyperkalemia. This is related to plasma osmolality.

High blood glucose levels increase the concentrate of the plasma. This creates force on the cells to release water into the extra-cellular space. Because potassium is the most abundant cation inside the cell, as the water flushes out, potassium is carried out too.

How closely related are BG and K levels?

In this, albeit old paper published in 1982, both blood glucose, serum sodium and potassium values were reported. This study included 193 individuals living with diabetes and taking insulin. They all had normal kidney function.

In the table below, you can see that BG levels above 10 were associated with increases in serum potassium.

The authors also reported that there was a linear relationship between blood glucose and serum potassium values.

The authors also tested the urine of the subjects. They reported that as blood glucose levels increased, so did urinary potassium and sodium. Consider that adults living with kidney disease may have impaired urine potassium excretion. Which is why individuals without kidney disease may not develop hyperkalemia, while adults with kidney disease will.

Take Aways

Ok, so when does the BG start to impact potassium levels? Easy answer – all the time. The higher the blood glucose level, the greater the pressure is for the potassium to be in the extra-cellular space. But, I will also give you this caveat that I have seen instances of high BGs and normal potassium levels. So I would look at the trend for your patient.

Is the potassium high now, if yes, what is their BG?

• If both are high and this is new, then I would correct the BG first and follow up on the K.
• If both are high, but the BGs have always been high and the potassium is new, I might focus more on diet to see if there have been any changes.

Literature Summary:

1. Several mechanisms increase the risk of hyperkalemia for adults living with diabetes.
2. Insulin brings both potassium and glucose into cells, not enough insulin = not enough glucose or potassium leaving the serum and entering the cells
3. In adults withOUT kidney disease there is a linear trend of increasing glucose levels and potassium levels, though levels may not always hit the hyperkalemia thresholds due to protective mechanisms in the kidney
4. In adults WITH kidney disease, this linear relationship also occurs, but the risk of hyperkalemia increases because of damage to protective mechanisms.