Urinary tract infections (UTIs) are among the most common bacterial infections treated in outpatient and inpatient settings. From primary care offices to urgent care clinics, providers see them daily — yet, billing errors and coding mistakes around UTI claims are still frequent.

Suppose your practice wants to reduce claim denials, improve documentation, and stay compliant with payer rules. In that case, this guide breaks down everything you need to know — from ICD-10 codes and documentation to billing guidelines, payer-specific notes, and best practices.

Urinary tract infections (UTIs) in Clinical and Coding Terms

Before diving into the code, let’s quickly ground ourselves in what a UTI includes.

A urinary tract infection (UTI) occurs when bacteria — most commonly E. coli — infect any part of the urinary system: kidneys, ureters, bladder, or urethra. Depending on the site, a UTI may be coded differently.

Clinically, UTIs fall into three main types:

• Cystitis: Infection of the bladder
• Pyelonephritis: Infection of the kidneys
• Urethritis: Infection of the urethra

Each type has its own ICD-10 coding pattern, and accuracy matters because the site and organism determine medical necessity and payer reimbursement.

Common ICD-10 Codes for UTI

Here are the most widely used ICD-10 codes providers use for urinary tract infections, depending on the site and cause:

1. N39.0 – Urinary tract infection, site not specified

• The most common UTI code is used when documentation doesn’t specify if the infection is in the bladder, urethra, or kidney.
• However, Medicare and commercial payers discourage using this unspecified code unless there’s genuinely no detail available.
• Always document the specific site when possible to avoid downcoding or denials.

2. N30.00 – Acute cystitis without hematuria

3. N30.01 – Acute cystitis with hematuria

• These codes apply when the infection is in the bladder.
• If the patient presents with blood in the urine, use the “with hematuria” variant.

4. N30.10 – Chronic cystitis without hematuria

5. N30.11 – Chronic cystitis with hematuria

• Used for recurrent or chronic bladder infections that persist or recur over time.

6. N10 – Acute pyelonephritis

• Indicates infection in the renal pelvis or kidney, often accompanied by fever, flank pain, and systemic symptoms.
• Patients expect supporting clinical evidence, such as lab reports or imaging results.

7. N11.0 – Chronic pyelonephritis

• For long-standing kidney infections or cases linked to structural abnormalities or reflux.

8. N34.1 – Nonspecific urethritis

• This applies to urethral infections, which are often seen in males but can occur in females too.
• Not to be confused with sexually transmitted infections like gonorrhea or chlamydia (which have separate codes).

9. O23.0 – Infections of the urinary tract in pregnancy, first trimester

O23.1 – Second trimester

O23.2 – Third trimester

• These codes are used for UTIs during pregnancy.
• Always code the trimester to ensure claim acceptance — missing it often causes claim rejections.

Coding Example ScenariosHere are some quick examples that reflect real-life encounters:Example 1:Scenario: A 27-year-old woman presents with dysuria and frequency. Urine culture confirms E. coli infection. Code: N30.00 – Acute cystitis without hematuria Additional code: B96.20 – Unspecified E. coli as the cause of diseases classified elsewhereExample 2:Scenario: 40-year-old male with flank pain and fever. Diagnosed with acute pyelonephritis caused by Pseudomonas aeruginosa. Code: N10 – Acute pyelonephritis Additional code: B96.5 – Pseudomonas (aeruginosa) as the cause of diseases classified elsewhereExample 3:Scenario: Pregnant woman, second trimester, diagnosed with UTI. Code: O23.1 – Infections of the urinary tract in pregnancy, second trimester

Billing Workflow for UTI Claims

A clean claim starts with a clean process. Here’s the billing sequence you should follow:

Verify Patient Eligibility

Confirm insurance coverage, plan limitations, and copay/deductible amounts before the visit.

Assign ICD-10 and CPT Codes Together

Link the diagnosis with appropriate CPT services such as:

• 99202–99215 — Office or outpatient E/M visit
• 81003 / 81001 — Urinalysis
• 87086 / 87088 — Urine culture

Always make sure the ICD-10 code supports medical necessity for these procedures.

Add Modifiers (When Required)

• Modifier 25: Use if you perform a separately identifiable E/M service along with a urinalysis or procedure.
• Use Modifier 59 if separate cultures or lab tests are billed on the same date.

Submit Claim with Supporting Documentation

Attach urine culture results or notes if the payer requires proof of infection.

Manage Denials

If denied, review:

• Diagnosis specificity (avoid “unspecified”)
• Missing organism code
• Incorrect linkage between CPT and ICD-10
• Mismatch between the pregnancy code and the patient record

Payer-Specific Rules

Medicare

• Covers diagnostic testing and E/M visits when medically necessary.
• Expects detailed notes for recurrent or chronic infections.
• Repeated UTI claims without documentation may trigger medical review.

Medicaid

• Coverage varies by state.
• Some Medicaid programs require prior authorization for imaging or repeat cultures.

Commercial Insurers (BCBS, Cigna, UnitedHealthcare, Aetna)

• Require linking UTI-related CPT codes (like 81003 or 87086) with specific ICD-10 codes (like N30.00 or N10).
• Claims are often denied if documentation lacks the infection site or organism.

Reimbursement and Fee Schedule For ICD-10 UTI

While rates vary by region, here’s a general reference:

Service	CPT Code	Approx. Medicare Reimbursement
Office visit, established patient (level 3)	99213	$90–$110
Urinalysis, automated	81003	$5–$10
Urine culture	87086	$20–$30

Note: These are approximate values from the Medicare Physician Fee Schedule (MPFS) and may differ by locality and payer contract.

Common Coding and Billing Mistakes (and How to Avoid Them)

UTIs might sound straightforward to diagnose and treat, but they’re one of the most commonly miscoded infections in outpatient billing. Many practices lose revenue not because of payer issues, but because of small, avoidable mistakes.

Let’s go through the most frequent UTI coding and billing errors — and how your team can fix or prevent them.

Overusing N39.0 (Unspecified Site)

Using N39.0 — “Urinary tract infection, site not specified” as a default code when documentation doesn’t clearly identify whether the infection is in the bladder, kidney, or urethra

Payers like Medicare and Blue Cross often flag this as non-specific. Too many claims with N39.0 can trigger audits or denials because the code doesn’t prove medical necessity for labs or antibiotics.

How to avoid it:

• Always document the exact site of infection (cystitis, pyelonephritis, etc.).
• Encourage providers to update EHR templates to include infection site fields.
• Use N30.00–N30.01 for cystitis or N10 for pyelonephritis whenever appropriate.

If you’re unsure of the infection site initially, use N39.0 for the first visit — but update the diagnosis once the urine culture identifies the location.

Missing B96 Organism Codes

Failing to include a causative organism code (B96.x) when a urine culture identifies bacteria like E. coli or Pseudomonas aeruginosa.

Organism codes validate the infection’s medical necessity. Many commercial payers require them for reimbursement, mainly when antibiotics are prescribed.

How to avoid it:

• Always review lab results before claim submission.
• Add the correct secondary B96 code to link the organism.
  • E. coli → B96.20
  • Pseudomonas aeruginosa → B96.5
  • Staphylococcus aureus → B95.2
• Set EHR reminders for coders to check lab reports for culture results before finalizing claims.

Example: Acute cystitis caused by E. coli → N30.00 + B96.20

Not Coding Trimester for Pregnant Patients

Using a general pregnancy infection code or UTI code without specifying the trimester (first, second, or third).

ICD-10 pregnancy-related infection codes (O23.x series) require trimester specificity. Missing this detail leads to automatic rejections by Medicare, Medicaid, and most commercial payers.

How to avoid it:

• Always ask and record the patient’s current trimester at the time of service.
• Use:
  • O23.0 – First trimester
  • O23.1 – Second trimester
  • O23.2 – Third trimester
• If the pregnancy stage changes between visits, update the code accordingly.

Always link the pregnancy complication code (O23.x) with the appropriate E/M or lab CPT codes on the same claim.

Failing to Append Modifier 25 for Same-Day Labs

Submit both an E/M (evaluation and management) visit and a lab test (e.g., urinalysis or culture) on the same day without modifier 25 attached to the E/M code.

Payers assume you’re double-billing for related services unless you clarify that the visit involved a separately identifiable evaluation beyond the lab itself.

Without modifier 25, they often pay only for the lab and deny the office visit.

How to avoid it:

• Append modifier 25 to your E/M code (e.g., 99213-25) when the provider performs both a clinical evaluation and lab testing in one visit.
• Make sure your documentation supports that the E/M service was distinct — not just the lab collection.

Example:

• 99213-25 (E/M)
• 81003 (urinalysis)
• N30.00 (acute cystitis)

Submitting Duplicate Claims Without Documentation of Recurrence

Sending multiple claims for the same patient and same diagnosis (UTI) within a short period without noting whether it’s a recurrent or new infection.

Insurance systems automatically flag repeat claims with identical codes as duplicates, assuming a billing error. This can delay payments or trigger audits.

How to avoid it:

• Update documentation for every new episode of care — note if it’s a recurrence or follow-up.
• For chronic cases, use N30.10–N30.11 or N11.0 instead of repeating acute codes.
• Include progress notes, lab results, and treatment changes to prove the new episode’s necessity.

If the second visit is for treatment follow-up (not a new infection), don’t bill a full E/M service unless medical necessity is documented.

Final Thoughts

UTI coding might seem simple at first, but the details matter — especially in billing. A single missing detail (like infection site or trimester) can turn a clean claim into a denial.

For providers and medical practices, the key takeaway is clear:

Document thoroughly, code precisely, and audit regularly.

Getting those three steps right ensures smoother reimbursements, fewer payer rejections, and more accurate clinical records.

Connect with SwiftCare Billing today