Yes, prednisone (a corticosteroid) may cause low potassium as a side effect.

The reason this happens is that corticosteroids send signals to the kidney telling it to retain sodium and lose potassium.

Low potassium related to prednisone use is usually easy to correct and rarely serious. Increased intake of foods that are high in potassium (such as bananas, orange juice, broccoli and spinach) or a potassium supplement can rapidly return potassium levels to normal.

It can be hard to know if low potassium is due to prednisone since there are many other causes, including:

• Other medications - Diuretics ("water pills") and laxatives are more common causes of low potassium than prednisone.
• Vomiting or diarrhea - Dehydration and electrolyte abnormalities, including low potassium, are common complications of frequent vomiting or significant diarrheal illness.
• Hyperaldosteronism - High levels of the hormone aldosterone tell the kidney to retain sodium and excrete potassium.
• Kidney disease - A condition called renal tubular acidosis may lead to the loss of potassium in the urine.
• Malnutrition - With adequate access to food, it's unusual to develop low potassium due to low intake. However, when overall food intake is poor, low potassium levels may develop.

If your potassium is low, talk to your doctor about the possible causes, including prednisone use, and how to get it back to normal.