After a UnitedHealthcare executive was gunned down on a New York City sidewalk, an eruption of bitter online commentary celebrated the killer’s presumed motive: avenging the denial and delay of health insurance coverage.

Many spoke from personal experience. Every year, health insurance companies deny tens of millions of patient claims for medical expense reimbursements, and the tide of those denials has been rising, according to surveys of doctors and other health-care providers. Insurers also have been increasingly demanding that doctors obtain approval before providing treatment, similar surveys show, causing delays in patient care that the American Medical Association says are “devastating.”

While several states have passed legislation trying to restrict such practices amid growing public anger, insurers defend the coverage denials and “pre-authorization” requirements. They say that those measures are meant to contain rising costs and that their methods comply with federal and state regulations. According to information the insurers report to regulators, there have been only small increases nationally in the frequency of denials in recent years.

Most frustrating, according to patient advocates, is that insurance companies often act without explanation, sending denial letters that offer only sparse justifications. The patient “gets a cryptic message saying ‘it’s not medically necessary,’ but without any other explanation,” said Elisabeth Benjamin, a vice president at the Community Service Society in New York, which runs a program that helps consumers appeal denials.

“People are mad because it’s all a big secret,” Benjamin said. “It’s unfair for us as a society, on something that’s so visceral, to trust giant corporations that make money when they deny care. This is why people are so, so very angry.”

Exactly why and how often claims are being denied or medical procedures are getting early scrutiny is difficult to know. Statistics regarding denials and pre-authorizations are scant, at best, and most of what is available reflects only one state or one type of insurance. Nationally over the last five years, the rates of denial have been between 14 percent and 16 percent, according to data from the National Association of Insurance Commissioners.

At least some state data, however, shows big increases. In Maryland, for example, regulators report that the number of claims denied by the insurers they regulate has risen nearly 40 percent since 2019.

Pointing in the same direction are large majorities of doctors and other health-care providers who report that insurers are denying more claims and imposing more pre-authorization requirements. For example, a 2024 survey conducted by Experian Health indicated that 73 percent of health-care providers said that “claim denials are increasing.” An American Medical Association survey similarly found that almost three-quarters of physicians said that denials of pre-authorization requests for treatment have increased over the past five years.

“The most common feelings I see are frustration and a sense of powerlessness,” said William Bennett, an associate professor at the Indiana University School of Medicine who studies patient experiences and treats children with chronic illnesses. “Patients have a relationship with their doctor. Their doctors know them, their doctors are experts in their disease, and then, for some reason that is never explained, the recommended care is denied.”

Insurance industry representatives blame doctors for many of the denials, saying they botch the required paperwork by submitting inaccurate, incomplete or ineligible claims information. In a statement last week, UnitedHealth said the company’s insurance division pays about 90 percent of medical claims when they’re submitted. Of the remainder that undergo additional review, only 0.5 percent are “due to medical or clinical reasons,” UnitedHealth said.

AHIP, a national association of health insurers, also issued a statement regarding denials, saying that “health plans are working to protect patients from the full impact of rising costs while connecting them to care that is safe, evidence-based and coordinated.”

Health-care providers have decried the requirements for prior authorization, which oblige doctors to request the insurer’s approval before providing patients with certain medical procedures and drugs. According to an AMA survey, nearly a quarter of physicians reported that these requirements led to an adverse event for a patient, and more than 9 in 10 physicians said the practice causes treatment delays. More than a quarter said their prior-authorization requests were often or always denied.

In response to such concerns, state legislatures have passed a raft of legislation. In 2024 alone, 10 states have passed bills aiming to cut what the AMA says is the “growing volume” of such requirements, to shorten the delays they cause, or to increase public reporting of data and procedures.

Only a small minority of patients appeal health coverage decisions, according to state and federal statistics. Many are daunted by the complexity of the medical terminology and the insurance bureaucracy.

“It’s hard to fight a big insurance company,” said Larry Levitt, executive vice president of KFF, a nonprofit health policy research and polling organization. “To even begin, you need to understand the gobbledygook in the paperwork. It’s hard to make heads or tails of it.”

In the Affordable Care Act, Congress authorized the establishment of Consumer Assistance Programs in the states to help people appeal denials of insurance coverage, but it has provided no funding for them in recent years. Even so, many states have set up offices to help.

Recent cases tackled by the Maryland attorney general testify to the range of arguments patients can have with their insurers. One patient experienced 30 percent visual impairment from eyelid inflammation and loose skin, but the insurer deemed the recommended surgery “cosmetic” and refused to pay. A 12-year-old received daily injections for a growth hormone deficiency for three years, but in the fourth year, the insurer deemed the shots not medically necessary and refused to pay. A patient having surgery to repair a broken clavicle unexpectedly needed work to repair a torn vein, but the insurer refused to pay for the extra procedure.

These denials would have forced each of those patients to pay thousands of dollars more than expected for needed care. After Maryland officials intervened, each of those consumers prevailed.

Last year, consumers in Maryland filed 11,466 challenges to denials. When a denial is challenged, consumers prevail about half the time, according to statistics from the state’s attorney general’s office.

But in Maryland, as in other states with programs to aid patients, officials say few consumers know that they can appeal a coverage denial, let alone that there is a program that can help them do so.

“We would love for more people to take advantage of this program,” said Marie Grant, Maryland’s acting insurance commissioner. “Insurance is inherently complicated, and I deeply understand the frustration here. But people don’t have to be alone in this journey.”