Be honest: you’ve lied about your weekly drink count at a doctor’s appointment. Probably more than once.

According to Dr. Ronald Epstein, a professor of family medicine at the University of Rochester Medical Center, this is a problem—and not just an ethical one. Writing for Vox via health journalist Dylan Scott, Dr. Epstein identified three categories of questions where patients lying or staying vague can have serious long-term consequences.

The first is the prescription medications someone is currently taking. The second is whether they’re taking those medications as directed. The third is whether they’re combining them with anything else, including alcohol, tobacco, or recreational drugs, and if so, how much and how often.

The logic is hard to argue with. Drug interactions are real, and some of them are dangerous. A doctor who doesn’t know you’re washing down your anxiety medication with a nightly bottle of wine can’t catch a problem developing in plain sight. “If the pills are something that if you miss a dose, you might suffer severe consequences, then it can be life and death,” Dr. Epstein said.

The gut check Dr. Epstein suggests for patients is simple: “Would withholding this information threaten or enhance the health of the person involved?” Most people, if they’re honest with themselves, already know the answer.

Lying to Your Doctor Isn’t Necessarily Your Fault

What’s notable is that Dr. Epstein didn’t put the entire burden on patients. He described honest medical conversations as a shared responsibility, and his read on the doctor-patient dynamic is more generous than most people who’ve sat in an exam room feeling interrogated would probably expect. Doctors, he argues, need to actively work to make patients feel safe enough to tell the truth.

“There are two aspects of any healing tradition,” he said. “One is the technical and instrumental pieces—the drugs you prescribe, the surgeries, the manipulations you do. The other is relational. That is the achievement of shared understanding, trust, confidence, and sometimes optimism so that people can really make decisions on their own behalf and feel empowered.”

In other words, if patients are lying to their doctors, that’s a two-way failure. Only one of them, though, is walking out of that appointment and rolling the dice on their own health.