“You don’t look well,” the man at the gas station told the older woman in the car. He’d known her for years, always thinking of her as a lively, robust woman. But that day she looked pale and tired. Her sharp blue eyes seemed dim. She gave a feeble smile. “I don’t feel well at all,” she told him.

There’s an urgent-care clinic just up the street, he said. Could she make it there? She was nearly 45 minutes away from her home in Halifax, Nova Scotia. Stopping just up the street seemed a much better option. At the clinic, the doctor took one look at her, put a blood pressure cuff around her arm and told her assistant to call an ambulance.

Surprising Blood Pressure

The rest of the day was a blur. The woman remembers being bundled onto a stretcher and one of the E.M.T.s saying her blood pressure was very low. It was an odd thing to hear, because her blood pressure was usually high enough to require three medications.

She was taken to the emergency room at the Queen Elizabeth II Health Sciences Center in Halifax. She remembers being fussed over — having blood drawn, receiving intravenous fluids, feeling sticky snaps being placed on her chest that connected her to a continuous heart monitor. She had been a nurse for many years when she was younger, yet seeing herself at the center of these familiar activities was strange. A blood test indicated that there may have been damage to her heart. The doctor told her she was having a heart attack, she recalls.

You’ve got the wrong patient, she thought to herself. Sure, she had a little high blood pressure, a little asthma, a little back pain. But problems with her heart? Never.

The next several days were filled with tests. Blood tests: normal except for the one that showed some sort of heart injury. An ultrasound of her heart: also normal. And finally a cardiac catheterization, a test to look at the vessels supplying blood to the heart for blockages that could cause a heart attack. After that test, the patient says, the doctor told her she had the arteries of a 35-year-old. Whatever had damaged her heart, it hadn’t been a heart attack.

Knocked Off Her Feet

While she was in the hospital, the patient was walking down the hall and suddenly felt lightheaded, as if she were about to faint. A nurse quickly took her blood pressure. It was quite low. Checked again a few minutes later, it was back to normal. Fainting is caused by inadequate blood flow to the brain. Her blood pressure had dropped too low to move the blood where it needed to go. Now the doctors needed to figure out why.

A quick review of the blood-pressure medications she took found a likely culprit. Doxazosin could cause blood pressure to drop rapidly, often after a change in position — a condition known as orthostatic (from the Greek for “standing upright”) hypotension. She had nearly fainted walking around after spending time in bed. Perhaps, somehow, something similar happened in the car as she drove, so that her heart, like her brain, had been temporarily starved of blood and oxygen. Her doctors stopped the medication.

Looking for a Cause

Throughout the summer the patient continued to have wild fluctuations in her blood pressure. She was worried, and so was her primary-care doctor. She was referred to a hypertension clinic at the hospital and saw Dr. Stephen Workman, an internist there.

This guy has style, the patient recalls thinking when she first met Workman. He was tall and slender and wore a pair of hip-looking glasses. She took two pills for her high blood pressure, she told the doctor, along with a handful of other medications: one for allergies, another for back pain and a couple of inhaled medications for her asthma. And she was very active. Although she used a cane, Workman noted that she had no difficulty getting up on the exam table — an important test of mobility. Her blood pressure that day was perfect. The rest of her exam was unremarkable. The doctor had already reviewed her records from the last few years — an easier task in Canada, where local records are consolidated — and found that she had anemia, a low red-blood-cell count. Her sodium, an important blood chemical, was also on the low side.

The drops in blood pressure, Workman thought, were probably because of yet another of the hypertension medications she was taking, a drug that lowers blood pressure by ridding the body of water. It can cause dehydration, which can, in turn, make blood pressure fall. It can also lower sodium. He told her to stop taking the medication.

To be safe, he ordered several tests — a couple to identify why she was anemic and one to look at her adrenal glands. Trouble with these glands is unusual but can cause both low sodium levels and episodes of low blood pressure. A problem was unlikely, but he wanted to be sure her adrenals were working.

Hormonal Issues

A few days later, the results came back. She had an iron-deficiency anemia — no shock there. But another test did surprise the doctor: Her cortisol, an essential fight-or-flight hormone made by the adrenal gland, was undetectable. Her adrenal glands were not working. There is a rare disease, Addison’s, in which the adrenal glands are wrecked either by infection or by a patient’s own immune system — John F. Kennedy had it. But a far more common cause of adrenal failure is the use of medicines that imitate the hormones the glands secrete — most commonly, steroids like prednisone, a synthesized version of the adrenal hormone cortisol. This patient didn’t take prednisone, but she did use the inhaled steroid fluticasone for her asthma.

It is clear that the oral version of these medications can turn off the adrenal gland, but it was thought that the advantage of inhaled steroids was that their effect was limited to the lungs and not the rest of the body. Over the last decade, though, new studies have shown that the drug can affect the adrenals of some patients as well, and Workman suspected that this woman was one of them.

Unintended Consequences

Inhaled steroids have saved many lives since they were developed in the 1960s and remain one of the most effective treatments for asthma. That’s why this patient took them. But she had never had pulmonary-function tests to see how severe her asthma was or whether the steroid medication was necessary. Workman worried that her body now depended on these inhaled hormones to replace the ones she was no longer making. She would experience symptoms only when there was some physiological stress on her body that would normally trigger the adrenal gland to secrete a higher level of stress hormone like cortisol to help her body deal with that stress. For example, she hadn’t eaten before she started to feel ill that day in the car. Her adrenals couldn’t respond, and so she ended up in the hospital.

An endocrinologist started the patient on a new pill to replace the hormones she wasn’t making. The plan is to wean her off the synthetic hormones when her glands recover. The patient had a pulmonary-function test, and her lungs were functioning well enough that she was taken off the inhaled steroids.

We think of medicines as the answer to a problem and not a cause. But more than 6 percent of all hospital admissions are because of adverse reactions to medications. And the level of benefit, as well as harm, can change with age. Up to 12 percent of patients over 65 who are admitted to the hospital are there because of some medication-linked problem. Older adults are at greater risk because the body’s ability to get rid of any medicine decreases with age. The patient, for her part, is eager to get this all sorted out. She has too much to do to spend this much time in doctors’ offices.