Ann Arbor, MI—The cost of insulin has gone up so much, tripling in a decade, that researchers are questioning whether the therapy is worth it, now that other effective diabetes drugs are available.

Prices for those other noninsulin diabetes prescriptions stayed about the same or even dropped from 2002 to 2013, according to a research letter published recently in JAMA.

Researchers from the University of Michigan and the University of Melbourne in Australia point out that, since 2010, the per-patient spending on insulin has been higher than that of all other diabetes drugs combined. They also add that competition from generics is not likely to lower the prices because of the regulatory environment.

The study used data from the federal Medical Expenditure Panel Survey, which asks patients and insurers about care and costs. Results indicate that the total cost of insulin more than tripled, from $231 a year to $736 a year for each patient, in 2013 dollars. At the same time, the cost per milliliter of insulin nearly tripled, from $4.34 to $12.92. In 2013, estimated expenditure per patient was $508 for analog insulin compared to $228 for human insulin.

Average annual usage, meanwhile, rose from 171 mL to 206 mL, as prescribed doses shot up. One explanation is that, as patients weighed more, a larger dose of insulin was prescribed. In addition, during the time period studied, there was a strong push to lower glucose levels for all people with diabetes.

“In the United States, the more than three-fold increase in the cost of insulin over the past decade is alarming. It is a burden to both patients and payers and may deny some people access to a lifesaving therapy,” said co-author William Herman, MD, MPH, a professor of internal medicine at the University of Michigan Medical School and of epidemiology at Michigan’s School of Public Health. “Although the newer, more expensive insulin analogs appear to have incremental benefits compared to older, less expensive insulin preparations, their premium price requires us to ask whether they are really necessary, and if so, for whom?”

Senior author Philip Clarke, PhD, a professor in Melbourne’s School of Population and Global Health and Centre for Health Policy, added, “What our study shows is how quickly things can change and why there is a need to focus on the costs as well as the benefits when deciding treatment options for people with diabetes.”

During the study period, the per-person spending on all other hyperglycemic medications was $502 in 2013, down from about $600 in 2002 in constant dollars, reached its lowest level in 2011, and has risen slightly since then.

The price of metformin, available as a generic, fell significantly from $1.24 per tablet in 2002 to 31 cents in 2013, while the cost of a newer class of drugs, DPP4 inhibitors, rose just 34% since they entered the market in 2006.

Of the 28,000 patients, average age 60, who received treatment for diabetes in the 11-year period, about a fourth used insulin to control their blood sugar, and two-thirds were taking an oral medication. At the end of the study, a small percentage began using new injectable drugs in conjunction with oral drug use.

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