Medical billing in the United States is extraordinarily complex. There are over 70,000 diagnosis codes, 10,000 procedure codes, and countless insurance plan variations. With that level of complexity, errors are not just possible — they are common.
Catching these errors can save you hundreds or even thousands of dollars. Here are the five most common medical bill mistakes and how to identify them.
1. Upcoding
What it is: Upcoding occurs when a provider bills for a more expensive service or procedure than what was actually performed. For example, a standard office visit (CPT code 99213) might be billed as a comprehensive visit (CPT code 99215), which costs significantly more.
How to catch it: Compare the service description on your bill to what actually happened during your visit. If you went in for a routine 15-minute checkup and the bill shows a 40-minute comprehensive evaluation, that is a red flag. Check your EOB — the procedure code should match the level of care you received.
What to do: Call the provider's billing department and ask them to review the coding. If they cannot explain the charge, request an itemized bill and dispute the code.
2. Duplicate Charges
What it is: Being billed twice for the same service, test, or supply. This happens more often than you might think, especially with hospital stays where multiple departments may enter charges.
How to catch it: Request an itemized bill (not just a summary statement) and look for identical charges on the same date of service. Pay attention to line items with the same CPT code, description, and amount.
What to do: Contact the billing department with the specific duplicate entries identified. Most providers will correct this quickly once it is pointed out.
3. Unbundling
What it is: When a provider bills separately for services that should be billed together under a single code at a lower total cost. For example, a panel of blood tests has a single bundled code, but a lab might bill each test individually at a higher combined price.
How to catch it: This one is harder to spot without billing knowledge. Look for multiple lab charges on the same date or several charges that seem related to a single procedure. The National Correct Coding Initiative (NCCI) published by CMS defines which codes should be bundled together.
What to do: Ask the billing department whether any of your charges should have been bundled. If you are unsure, contact your insurance company — they have systems designed to catch unbundling.
4. Incorrect Patient Information
What it is: Errors in your name, date of birth, insurance ID number, or policy details can cause claims to be denied or processed incorrectly. Even a single wrong digit in your member ID can result in you being billed the full amount.
How to catch it: Review the patient information on every bill and EOB. Make sure your insurance details are correct. If a claim was denied, check whether the denial was due to an "unable to identify subscriber" or similar administrative reason.
What to do: Contact the provider with your correct information and ask them to resubmit the claim. This type of error is almost always correctable.
5. Balance Billing for In-Network Services
What it is: Balance billing happens when a provider bills you for the difference between their full charge and what your insurance paid. For in-network providers, this is generally not allowed — they have agreed to accept the insurance company's negotiated rate as payment in full.
How to catch it: Compare the "amount billed" on your EOB to your actual bill. If an in-network provider is charging you more than the "patient responsibility" amount shown on your EOB, they may be balance billing you. Note: the No Surprises Act (effective January 2022) also protects you from balance billing in many emergency and out-of-network situations at in-network facilities.
What to do: Contact the provider and reference your EOB, pointing out that the patient responsibility amount is lower than what they billed you. If they refuse to correct it, file a complaint with your state's Department of Insurance.
What These Errors Cost You
Even a single billing error can cost hundreds of dollars. A hospital stay with upcoding and unbundling errors can inflate your bill by thousands. Because most people pay their medical bills without questioning them, these errors often go undetected.
How Lysco Can Help
Lysco analyzes your medical bills line by line, comparing charges against fair market rates and checking for common errors like the ones described above. Upload your bill at lysco.com and get a clear breakdown of what looks right, what looks wrong, and what to do about it. Analysis is always free.
Sources: National Correct Coding Initiative (CMS), No Surprises Act (Public Law 116-260), American Hospital Association billing guidelines, CPT code reference (AMA).