Chapter 9: Medical Testing Secrets

What You Need To Know And Do When Your Doctor Orders Tests

May 30, 2025

Testing error has harmed too many lives and much of it is preventable. It was the cause of famous stories of misdiagnosed cancers like Patrick Sheridan (he died of cancer because the test result was misplaced) and Lisa Monk (she endured 15 months of chemotherapy for a non-existing cancer). It was the cause of two of my son’s misdiagnoses –– one lasting for over 8 years –– and of my unnecessary breast cancer surgery.

As I wrote in Chapter 1, testing error is the number one cause of misdiagnosis, contributing to 70% of diagnostic mistakes. Errors can happen at every step, from ordering, collecting, processing, obtaining results, or communicating results. It can affect every kind of medical test: blood, urine, imaging and more.

So, how can patients protect themselves from testing errors? There’s actually a lot we can do with minimal effort. Let’s start with understanding how things go wrong in the first place.

How Do Testing Errors Happen?

Think of medical testing as a relay race of sorts with your test sample passing from one person to another. With every handoff, in every step, there is the possibility of an error. Miraculously, considering the 14 billion clinical lab tests conducted each year in the US, it works most of the time.

There are four major types of mistakes. You have a measure of control over the first three:

Identity errors (~ 20%) mean someone else’s name is on your sample, or your name on your urine test is illegible, or two patients are scheduled back to back on a busy day and their results get mixed up. Check every blood or urine sample to see it has your name and birthdate on it. Use your voice for other kinds of tests. Once she learned her friend’s scheduled test was performed on her hospital roommate, my mom would introduce herself to every orderly and nurse that walked into her hospital room and ask, “Are you sure you’re here for me?”
Lack of follow-up is another big cause of error (~21.5%). The lab or the doctor’s office simply drops the ball. Tests can get lost in the system like Pat Sheridan’s. Or the doctor never gets to review the results so she never reaches out to you to discuss next steps. Missed cancer diagnoses were the most common negative outcome of failure to follow up. You have some power here. Lucky you, there’s a recent federal rule that all test results are reported to the patient via the patient portal the same time they’re reported to the doctor. You’ll get an email IF you joined the patient portal. Not enough of us do. Join all the portals!! It’s important to have access to the actual results for second opinions or if you want to research on your own. (See Pro Tips for more)
Human error — the doctor’s and yours — represents about 35% of testing mistakes. I wrote about cognitive biases and errors in Chapter 1. They are why doctors may order the wrong test, not order the right one or depend too heavily on the test results. If the doctor chooses the wrong tests, especially if you have autoimmune disorders or endometriosis, you can still be seriously ill despite all your test results being fine. Other errors of judgment may be due to burnout or training gaps, like misunderstanding test results. You can contribute to this type of error or you can fix it. Know how to prepare for every test and which activities, medicines, supplements or foods you need to avoid before. [See How Can I Avoid Contributing To Testing Errors #3 and #4 below.]
Technical or processing problems (~23.5%). Many of these you have no control over, like a poorly trained technician using the equipment incorrectly or a nurse who doesn’t know a specific test requires him to both spin the blood sample and freeze it before sending it to the lab.

The Ideal Scenario For Avoiding Testing Errors

Medical testing ought to happen only after a complete history is taken and a physical exam is given. The doctor should ask lots of questions about your symptoms, your medical history, your family’s medical history, and listen to your answers without interruption. Hopefully, you used all the tools I provided you in Chapter 2 and in Chapter 7.

Next, they should examine you physically –– listen to your heart, your chest, examine your ears, eyes, nose, your reflexes, with special attention to where your concerns lie –– and then ask more questions. Based just on these elements, they can create what is called a diagnostic differential, a list of the most likely and the most dangerous possible causes.

Then and only then, should they create a list of the tests they need to help narrow down the list of diagnoses and to rule out the scary ones. Ordering lots of tests is less time consuming and more profitable than conducting a thorough history and clinical exam. If your doctor routinely skips the history and exam, find another doctor.

How Can I Avoid Contributing To Testing Errors?

There are 6 questions you need answered before you get tested.

Before they order any tests, the doctor should discuss them with you so you understand what tests are ordered, why, and how to prepare for them. Here is a list of six things the doctor should tell you –– or you should ask –– before any testing is done.

What tests(s) will you order? Ask for a copy of the orders or write them all down so you can check later.
Why do I need this test? Each test can have several purposes. Some are to screen you for common diseases, some are to rule out serious conditions, some are exploratory. Not every test is essential. You have the right to ask whether the test is necessary and safe. If it’s costly, invasive, or if there are any risks, ask if there’s an alternative.
How do I prepare for this test? This is perhaps the most important question you can ask. If you don’t prepare properly, you’ll waste your time and money, and get misdiagnosed. Some require fasting before or skipping medications. One example are routine cholesterol blood tests which can give false results if you take diuretics, birth control pills, corticosteroids (which are a common class of anti-inflammatory) and some antibiotics. Ask the doctor to write down the instructions for you.
Are there foods or supplements I need to avoid beforehand? I hope you’ve already entered the Medical ID infoin your phone with your list of supplements. They’re often the source of inaccurate test results. For example, Biotin (B7), a vitamin present in most multivitamins and products for improving hair, nails, and skin, can cause false high and low scores and lead to treatment for the wrong condition. Food and drinks to avoid before tests can include high fat foods, meat, caffeine, alcohol, sugary drinks, and hold off on sex, drugs and rock ‘n roll the night before.
How do I schedule these tests? If your insurance requires precertification for the test, the medical practice should deal with it and then have the testing facility call you to schedule. Call them back. Sometimes, the practice will give you the lab or facility’s phone number so you can schedule it yourself.
When will I get the results? The doctor will have an estimate but no exact dates so ask the various lab techs this question. Keep a list of all the tests you have completed. if you don’t hear the results when you’re supposed to, call the practice and ask where it is.

What Happens Next?

Talk to your doctor about test results, in-person or virtually.

Once the results are in, you should meet with the doctor again, in person or virtually, to discuss the results, what they mean, what additional tests might be needed, and to ask questions.

Be aware, few tests have simple “Yes” or “No” answers. Most lab tests are compared to an established reference range from healthy people. Your doctor will explain if your results are higher, lower, or within the range and what that means.

Test results can be misleading. The reference ranges generally represent typical white males 21-45, so they may not apply to all ages, races, and ethnicities. Also, some autoimmune diseases, like rheumatoid arthritis (RA) or Lyme Disease, are plagued by negative results. For example, there are blood tests that can help diagnose RA, but only 85 percent of RA patients ever test positive for that factor. To make an accurate diagnosis, the doctor needs to rely on more clinical details like family history, which joints are involved, when it began, and how long it lasts.

PRO TIPS

Remember, test results are NOT diagnoses. They’re clues to your diagnosis.
No news is no news. You may think no news is good news. It’s not true. A missing test can cause you harm.
If your doctor wants her lab tech to draw your blood before you leave, ask first if any of the tests require fasting, avoiding supplements or certain foods first. There’s no additional cost to prep and return another day.
Getting tested for cancer or something else scary? Make sure you have a follow up appointment –– in person or virtual –– scheduled in advance for a day or two after that result is due. Also, you can turn off the portal email alerts for those tests or request the practice does it. It can be traumatic learning you might have cancer without the doctor’s guidance.
Curious about the results before you see the doctor? Upload your test results to your favorite AI like ChatGPT or CoPilot. They’re great at explaining what the tests mean. But first, remove your name, address and birthdate to ensure privacy. We’ll cover this in greater detail soon.
Wary of using AI? Read the report. You can learn a lot. I like Medline to explain most lab tests. For imaging test reports, like CTs, MRIs, and ultrasounds, check out this website run by the Radiological Society of North America, Inc. (RSNA). They explain the different types of tests and help you to read and understand your imaging test report.
Ask your doctor if the lab uses patient-centered pathology report (PCPR) formats, which present the results in plain language. Pathologists can generate a PCPR in just a few minutes using a preexisting template.

Next Up: Chapter 10: Gaslighted, Dismissed or Ignored By Your Doctor? Nine Ways To Make It Stop.