This story has been updated to clarify that over-the-counter insulin formulations have changed from animal-based to a synthetic human version since the product first was introduced in the 1950s.

As drug prices continue to rise, patients who can’t afford their medicine are taking some truly drastic steps.

Some travel across borders or order through international online pharmacies, where medications commonly retail for much less. Others try to ration or skip doses.

Researchers at Christiana Care Health System in Delaware set out to learn more about over-the-counter insulin, a medication created nearly a century ago that people may be turning to if soaring insulin prices are placing modern medicines out of their reach.

Insulin has been available over the counter, without a prescription, since the 1950s, though it’s not a widely known product and is difficult to use safely, especially without the close guidance of a physician. It retails for a fraction of the price of the newer, analog insulins that are now commonly prescribed. These are laboratory-grown versions of the naturally occurring hormone that are genetically altered to act more rapidly or uniformly than the synthetic varieties.

Walmart-brand ReliOn human synthetic insulin is available without a prescription in every state except Indiana, and retails for a fraction of the cost of brand-name analog versions, making it popular among some patients who can’t afford the pricier versions their doctors prescribed, according to the researchers’ findings, published in a research letter in JAMA Internal Medicine on Monday.

Researchers surveyed 582 Walmart and other chain pharmacies about their sales and customers.

Just over half of the 557 pharmacies that completed the survey were Walmart pharmacies. Among them, 87 percent said they sold over-the-counter insulin daily. Non-Walmart pharmacies reported infrequent over-the-counter insulin sales.

Fifty-five percent of the pharmacies surveyed said they were aware of patients who purchased over-the-counter insulin because they could not afford their prescription insulin.

But some nonprescription products are more affordable than others.

A 10 milliliter vial of ReliOn costs $24.88, compared with between $152 and $163 for a vial of Novolin or Humulin, over-the-counter human insulins sold at other pharmacies, according to the report.

Brand-name insulin analogs can cost twice as much. A vial of Norvo Nordisk’s Novolog, which requires a prescription and does not have a generic equivalent, costs more than $300, according to GoodRx, a website that tracks drug prices by pharmacy.

“Many patients with diabetes are struggling to afford their medication. The availability of insulin over the counter is potentially a solution for some patients but doesn’t come without potential consequences, especially for patients who do not have access to a health-care provider to help use that medication safely,” said lead author Jennifer N. Goldstein, a doctor and assistant program director of internal medicine at Christiana Care System.

Human and synthetic insulins are not the same, which mean substituting one insulin without a doctor’s input could be dangerous. Goldstein cautioned that patients should not swap one type of insulin for another without talking to their doctor.

The original forms of insulins sold over-the-counter predate federal drug prescribing regulations established in 1951 and have continued to be available without a prescription since then.

These days, patients are more commonly prescribed a combination of analog insulins that help keep blood sugar levels even throughout the day. They’reconsidered easier to use and more predictable, Goldstein said.

Human insulins like ReliOn don’t last as long and must be taken more often. Patients report having to diligently monitor their blood sugars, and stick to a strict dietary regimen of precisely timed and composed meals.

While the pharmacy survey found that this type of insulin is being purchased, it’s unclear whether it is harming their health.

“It’s really unclear whether over-the-counter insulin is associated with better or worse outcomes for patients because there’s no data,” Goldstein said. “The next step is really to try to examine use and outcomes.”