There’s a pesky cognitive bias that creates a honking big barrier to patients and families making the most of the health advice and services available to us. It’s the tendency of experts to overestimate the knowledge of others.

One consequence of expertise — or even just easy familiarity with a topic or institution or practice — is the inability to remember not knowing what you now know. Think back to your first day of school: You felt clueless, right? Was I supposed to bring crayons? Where’s the bathroom? But within weeks, the whole thing was routine. You couldn’t remember what you didn’t know, and you couldn’t recall what you might have needed to know in order to concentrate on learning to spell.

Given my current, frequent brushes with health care, I experience this all the time: “Just go to the lab and ask them,” I’m told by my chemo nurse. I think: Huh? What lab? Where? Ask who? As my oncologist walks out the door, he says, “You should take folic acid to prevent side effects.” I think, sure. When? How much? Do I need a prescription? Will you write it? And the practice staff assures me, “Oh, you can ask any of us about your symptoms.” Who is ‘”us”? How do I get in touch with each of you? Will each of you know about me? What will you know? What if I only want to talk with you specifically?

There is a rich literature about the extent to which physicians, nurses, health plans and employers overestimate their constituents’ knowledge about health concerns:

• Physicians vastly overestimate patients’ knowledge of the process of informed consent.
• Doctors and nurses frequently overestimate their patients’ health literacy.
• Clinicians overestimate the amount of information they give to patients about medication.
• Many health websites for the public assume a 9th- to 14th-grade reading level.
• Many people don’t know the location of key organs (e.g., heart, lungs), even those in which their medical problem is situated.

The effects of these health stakeholders’ overestimation of our knowledge are profound. This is a matter of what information we need, not just how or if we learn it (health literacy). Its impact is reflected in miscommunications ranging from the poor design of hospital signage to the lack of explanations about what it means to be cared for by a primary care team. You can find its impact in pink pamphlets about how to prepare for surgery and the sparse information we receive about how to get after-hours care.

Most of us are mostly well most of the time. And so when we seek care, we often find ourselves lacking the knowledge we need to accomplish health care-related tasks efficiently and effectively. As health care becomes more complex, with more options, providers and interventions, more responsibility for caring for ourselves and our loved ones falls to us. Simultaneously, the stakes of our abilities to make good use of those advances rise, as does our need for a range of very basic information and guidance to help us perform health tasks the best we can.

I know it is brutally expensive to do the kind of basic consumer research on every patient portal, website and pamphlet to find out what we need to know in the way that successful corporations do to attract and inform customers. And it is wildly difficult to convince professionals of all stripes that we need this kind of basic information and guidance — and thus to spend time making sure we really understand what’s going on and what and how to do something about it. Indeed, the overestimation bias among health professionals and other experts prevents them from recognizing the scope of this problem — our knowledge needs — and thus in allocating resources to solving it.

Maybe in our current cost-conscious environment, the cheap old “let ’em sink or swim” approach is preferable to addressing a well-known, well-documented bias that mostly disadvantages our participation in our own care. We are, after all, a pretty resourceful bunch, us patients. Many of us will figure it out. But there are many of us who, for a variety of reasons, simply lack the resources to ask, to explore, to persist until we are both competent and confident to care for ourselves and those we love. We pay a high price for those pinched pennies.

Jessie Gruman is the founder and president, Center for Advancing Health. She is the author of Aftershock: What to Do When You or Someone you Love is Diagnosed with a Devastating Diagnosis. She blogs on the Prepared Patient blog.