Q. My mother was prescribed HCTZ for high blood pressure. Her potassium and sodium levels had not been tested in three years, although she saw her doctor for yearly checkups. She ended up in the hospital for three days due to incredibly low sodium levels.

At the time, the area was in a heat wave with very high temperatures and humidity. She was sweating and drinking water to stay hydrated. All of this worked together to cause the dangerously low sodium and potassium levels.

Her hands were beginning to shake. We were lucky she didn’t have a seizure or die. The hospital doctors took her off HCTZ.

A. Potassium and sodium are critical minerals. The body tries hard to keep both in balance, but some medications can interfere with that outcome.

If sodium levels drop below 135 mEq/L, people may develop serious symptoms, including confusion, muscle cramps, weakness, loss of appetite and nausea. When potassium levels fall below 3.5 mEq/L people may develop similar symptoms. These can include muscle cramps, confusion, fatigue, weakness and irregular heart rhythms.

Hydrochlorothiazide (HCTZ) can deplete the body of both sodium and potassium. You can learn more about the effects of various antihypertensive medicines in our “eGuide to Blood Pressure Solutions.” This online resource is located under the Health eGuides tab at www.PeoplesPharmacy.com.

Drinking a lot of water in hot weather may contribute to both low sodium and low potassium, especially if there is a diuretic on board. Electrolyte-containing beverages might be safer at this time of year.

Q. I have been taking prednisone since 2008 for an autoimmune disease, and I may spend the rest of my life coping with the adverse effects. The major problem now appears to be osteoporosis.

My rheumatologist has suggested Forteo or Tymlos to treat the bone loss. I worry about side effects, especially from the bisphosphonate I would need to take after a few years. Why aren’t we warned about the complications of prednisone before we start taking it?

A. Prednisone is a corticosteroid that can help ease inflammation from a variety of sources. Long-term use, however, can weaken bones. That is why your doctor has recommended treatment for osteoporosis. After taking either Forteo or Tymlos, you would most likely need to take a bisphosphonate like alendronate to maintain bone strength. Doctors should always mention potentially serious side effects when offering any prescription.

Q. I got stuck in an airport for a six-hour layover. Not wanting to sit still for all that time, I walked circuits around the terminal. Unfortunately, I was not wearing the proper shoes and developed blisters. Can you suggest a blister remedy that I can pack in my carry-on to prevent this from ever happening again?

A. Our favorite product to prevent blisters is a hydrocolloid from Spenco called 2nd Skin Blister Pads. The box should fit in your hand luggage.

A report in Wilderness & Environmental Medicine (September 2019) describes the use of a similar hydrocolloid dressing for a serious blister experienced by someone climbing Mount Everest. According to the authors, “The Wilderness Medical Society wound care guidelines recommend that blisters larger than 5 mm should be drained but the roof left intact. The blister should then be covered with a hydrocolloid or hydrogel patch or equivalent, such as petrolatum or antibacterial ointment covered with gauze or moleskin.”

In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of King Features, 300 W. 57th Street, 41st Floor, New York, NY 10019, or email them via their website: www.PeoplesPharmacy.com. Their newest book is “Top Screwups Doctors Make and How to Avoid Them.”