How to Review Your Medical Bill: A Step-by-Step Guide

If you’ve ever opened a medical bill and felt a knot in your stomach, you’re not alone. The average American household carries $4,600 in medical debt Source, and much of that debt may include charges that are flat-out wrong. Studies show that up to 80% of medical bills contain errors Source - yet fewer than 1% of patients ever review their bills Source.

The good news? You can fight back. This guide walks you through eight steps to review your medical bill, spot errors, and dispute overcharges. And if you want the process done in minutes instead of hours, NilesAI can do it for you.

Step 1: Gather your documents

Before you can review anything, you need the right paperwork. There are two critical documents:

The Explanation of Benefits (EOB) - This is the statement your insurance company sends after processing a claim. It shows what the provider billed, what insurance paid, and what you owe. If you haven’t received yours, log into your insurance portal or call the member services number on your insurance card. (Our complete guide to understanding your EOB breaks down every section.) If you received care in an emergency room, you may have multiple bills from different entities - our ER bill anatomy guide explains how to match each bill to the right EOB.

The itemized bill - This is different from the summary bill most providers send. An itemized bill lists every single charge - each procedure code, each medication, each supply - with individual prices. Most providers don’t send this automatically. You have to ask.

Step 2: Check the basics

Start with the simple stuff. Errors in patient demographics are more common than you’d think, and they can lead to charges for someone else’s care ending up on your bill.

Verify:

• Your name and date of birth - typos can cause records to merge
• Dates of service - do they match when you were actually seen?
• Provider name - is this the doctor or facility you actually visited?
• Services listed - scan for any procedure or test you don’t recognize or didn’t receive

If you see a service you never received, flag it immediately. This is one of the most common billing errors and can be worth hundreds or thousands of dollars.

Step 3: Compare charges to your EOB

This is where many overcharges hide. Place your itemized bill and EOB side by side and compare:

• Billed amount (what the provider charged) vs. Allowed amount (what your insurance agreed to pay)
• Patient responsibility - does the amount on your bill match what the EOB says you owe?
• Adjustments - did the provider properly discount the difference between billed and allowed amounts?

If your provider is in-network, they’ve agreed to accept the insurance company’s allowed amount. They cannot bill you for the difference - this is called balance billing, and it’s prohibited for in-network providers in most states and under the No Surprises Act for emergency services and certain other situations.

Step 4: Look up the codes

Every line item on your itemized bill has a CPT code (Current Procedural Terminology) or HCPCS code that identifies the specific service. These codes are maintained by the American Medical Association and CMS.

For each code, ask yourself:

• Does the description match what actually happened? A code for a “complete office visit” (CPT 99215) when you had a brief follow-up (CPT 99213) is called upcoding - and it’s one of the most common forms of billing fraud according to the HHS Office of Inspector General.
• Are there codes you don’t recognize? Look them up on CMS.gov, your insurance company’s website, or our medical billing glossary. You can also look up Medicare rates for common procedures to see what a fair price looks like.
• Are procedures bundled correctly? Some services should be included in the price of another service under CMS NCCI bundling rules. For example, a surgical tray (CPT 99070) is typically bundled into the primary surgical procedure. If it’s billed separately, that may be an error.

Step 5: Check for duplicates

Scan your bill for the same service billed on the same date. Duplicates happen more often than you’d expect - especially with electronic billing systems that can accidentally submit a charge twice.

Look for:

• Identical CPT codes on the same date of service
• Very similar services (e.g., two versions of the same lab panel)
• The same charge appearing under slightly different descriptions

Hospital bills with 50+ line items are particularly prone to duplicates. Our whitepaper on medical billing errors found that duplicate charges account for a significant portion of billing errors in inpatient stays. If you have a complex bill with multiple line items, our step-by-step guide to imaging and lab overcharges covers the specific duplicate and unbundling patterns most common in diagnostic charges.

Step 6: Verify the math

It sounds basic, but add up the line items yourself. Check that:

• Individual line items multiplied by their units equal the extended amount
• The total of all line items equals the bill total
• Any payments or adjustments are correctly subtracted
• Units billed are reasonable - for example, if you were in the hospital for 2 days, a charge for 5 days of room and board is clearly wrong

CMS maintains Medically Unlikely Edits (MUEs) that set maximum units for each procedure code. While these are designed for Medicare claims, they’re a useful benchmark for spotting excessive units on any bill.

Step 7: Know your rights

Federal and state laws protect you from unfair billing practices. Key protections include:

The No Surprises Act - Effective January 2022, this law protects you from surprise out-of-network bills for emergency services, air ambulance services from out-of-network providers, and certain non-emergency services at in-network facilities. Learn more at CMS.gov/nosurprises.

State insurance commissioner - Every state has an insurance department that handles consumer complaints. If your insurer denies a legitimate claim or your provider engages in balance billing, file a complaint. Find your state’s office through the National Association of Insurance Commissioners.

Appeal rights - Under the Affordable Care Act, you have the right to appeal any insurance denial. You can request an internal review and, if that fails, an independent external review.

Fair billing protections - The Patient Advocate Foundation offers free case management services and can help you work through billing disputes, insurance denials, and financial hardship programs.

Step 8: Dispute what’s wrong

Once you’ve identified errors, it’s time to take action. Here’s who to contact and what to say:

Start with the provider’s billing department. Call the number on your bill and explain the specific errors you found. Be clear and factual - reference the CPT codes, the dates, and the dollar amounts.

Follow up in writing. Phone calls are a start, but a written dispute creates a paper trail. Here’s a template:

For a printable version of this review process, download our medical bill review checklist. And if you need help with the negotiation conversation itself, we have word-for-word scripts you can use when calling your provider.

Escalate if needed. If the billing department doesn’t resolve the issue within 30 days:

1. File a complaint with your state insurance commissioner
2. Submit a complaint to the Consumer Financial Protection Bureau if the debt has been sent to collections
3. Contact the Patient Advocate Foundation for free assistance
4. For bills over $10,000, consider hiring a professional medical billing advocate

The faster way: let NilesAI do it

Everything in this 8-step guide - verifying codes, checking for duplicates, comparing charges to fee schedules, flagging bundling violations - is exactly what NilesAI’s 16 scan engines do automatically.

Instead of spending hours cross-referencing your bill against CMS databases, you can:

1. Upload your itemized bill (and your EOB for even deeper analysis)
2. Wait minutes while NilesAI runs all 16 validation engines
3. Review findings - every error is cited with the specific rule it violates and the dollar impact

NilesAI checks your bill against 2.6 million NCCI edit pairs, 7,700+ Medicare fee schedule rates, 16,600+ active HCPCS codes, and 10,500+ MUE unit limits. No CPT code goes unchecked. No bundling violation goes unnoticed.

Whether you’re reviewing a $500 office visit or a $150,000 hospital stay, NilesAI gives you the same thoroughness that a professional billing auditor would - in a fraction of the time and at a fraction of the cost. For a complete overview of the entire review process, including how to interpret your findings, see our Medical Bill Review Guide.

You can scan a bill for free now to see what NilesAI finds.