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When you think about blood sugar, potassium may not be the first thing that comes to mind. But this mineral helps your pancreas release insulin—and insulin helps decide where potassium goes in your body.
When potassium gets too low, that relationship can make blood sugar harder to control.
In this episode of Metabolic Classroom, Dr. Ben Bikman explains how potassium, insulin, and a hormone called aldosterone work together. He also explores what this means for blood pressure, everyday food choices, and the changes that happen during a prolonged fast.
How Insulin Moves Potassium
Most of the potassium in your body is inside your cells. Only a small amount circulates in your blood.
Insulin helps move potassium from the blood into cells, particularly muscle cells. After a meal, this helps keep blood potassium within a safe range while the kidneys adjust how much potassium leaves the body.
This effect can remain active even in insulin resistance. A person’s cells may respond less effectively to insulin’s signal to take up glucose while still responding to its signal to take up potassium.
Moving potassium into cells is different from losing it from the body. That distinction helps explain why a blood test does not tell the whole story about potassium stores.
Why Low Potassium Can Raise Blood Sugar
Potassium also affects how well the pancreas releases insulin.
In a small experiment discussed in the episode, researchers deliberately depleted potassium in seven healthy men. Afterward, the men released less insulin and cleared glucose from their blood less effectively. Their tissues’ sensitivity to insulin did not change.
That distinction matters. Blood sugar can rise because the body releases too little insulin, because tissues respond poorly to insulin, or because both problems are present.
These findings help explain how low potassium can worsen glucose control. They do not establish that taking extra potassium will prevent diabetes or improve blood sugar in everyone.
Where Aldosterone Fits In
Insulin does not manage potassium alone. Aldosterone, a hormone made by the adrenal glands, tells the kidneys to retain sodium and release potassium into the urine.
When aldosterone runs too high, the body can lose too much potassium. It can also retain more sodium and water, contributing to high blood pressure.
Dr. Bikman reviews evidence that excess aldosterone may reduce insulin release both through potassium loss and through effects on the pancreas itself. Some of that evidence comes from small human studies and laboratory research.
Persistently low potassium alongside high blood pressure—especially blood pressure that is difficult to control—is a reason to discuss aldosterone testing with your healthcare provider.
What Your Potassium Test Can Tell You
A blood test measures the potassium circulating in your bloodstream. Because most potassium is stored inside cells, that result is not a complete measure of the body’s supply.
Dr. Bikman discusses research linking potassium levels at the lower end of the normal range with a higher risk of developing type 2 diabetes. These observational studies show an association; they do not prove that raising potassium prevents diabetes.
A low or repeatedly low-normal result is worth discussing in context with your clinician, including your medications, kidney function, and blood pressure.
Magnesium matters, too. Low magnesium can make the kidneys lose more potassium, making a potassium deficiency harder to correct.
Why Prolonged Fasting Changes The Picture
When you stop eating, insulin falls. The kidneys release more sodium and water, and changes in aldosterone can affect how much potassium is lost.
When eating resumes, insulin rises and moves potassium back into cells. After prolonged food deprivation, depleted stores can make that shift more dangerous. Phosphate and magnesium can fall as well.
In people who are malnourished or have eaten little or nothing for several days, these changes can contribute to refeeding syndrome, a potentially serious condition. This is different from an ordinary overnight fast.
Anyone considering a multiday fast should discuss it with their healthcare provider, particularly if they take insulin, diabetes medicines, diuretics, or blood pressure medication. After prolonged food deprivation, restarting food may require clinical monitoring; choosing a particular meal does not eliminate that risk.
Practical Steps For Metabolic Health
The goal is to support a healthy potassium balance. More is not always better, and supplements are not a proven way to prevent diabetes.
- Include potassium-containing whole foods. Vegetables, beans and lentils, dairy, meat, and fish can all contribute. Choose foods that fit your eating pattern and any guidance you have received about kidney health.
- Ask about persistent low potassium. Your clinician can help identify possible causes, including medication effects and excess aldosterone.
- Check before using supplements or potassium-based salt substitutes. Kidney disease and medicines such as lisinopril, losartan, or spironolactone can allow potassium to build up to unsafe levels.
The NIH’s potassium fact sheet provides more information about food sources and medication interactions.
Watch the video or listen to the podcast above as Dr. Bikman explains why potassium deserves a place in the conversation about insulin, blood pressure, and metabolic health.