How much does antimicrobial susceptibility testing (CPT 87186) cost?

Antimicrobial susceptibility testing by MIC method (CPT 87186) averages $53.73 per charge. Medicare pays approximately $8 to $12 under the Clinical Laboratory Fee Schedule. This charge is in addition to the bacterial culture itself, which is billed separately.

CPT (Current Procedural Terminology) codes are five-digit numbers that describe every medical service or procedure. Your doctor, hospital, and insurance company use them to communicate exactly what was done. Every line on your medical bill has a CPT code, and knowing the code lets you look up what Medicare pays for that same service.

Why do providers charge so much more than Medicare pays?

Providers set their own "chargemaster" prices, which are essentially list prices. Medicare pays a fixed rate based on the resources each service actually requires (the RVU system for procedures, or the Clinical Lab Fee Schedule for lab tests). Commercial insurers typically pay 150% to 250% of Medicare rates. Uninsured patients are often billed the full chargemaster price, which can be 2x to 30x what Medicare pays.

Can I use Medicare rates to negotiate my bill?

Yes. Medicare rates are the closest thing to a "fair price" benchmark in U.S. healthcare. When negotiating, ask the provider what they accept from Medicare for the same CPT code. Most providers will accept 150% to 200% of Medicare for cash-pay patients, which is still far less than their chargemaster price. Many hospital financial assistance policies also use a multiple of Medicare as their discount floor.

How are Medicare rates calculated?

For most procedures, Medicare uses the Resource-Based Relative Value Scale (RBRVS). Each CPT code gets three RVU components: Work (physician time and skill), Practice Expense (overhead), and Malpractice. These are multiplied by geographic adjustment factors (GPCIs) and a conversion factor ($33.4009 in 2026). Lab tests (80000-89999 range) use a separate Clinical Laboratory Fee Schedule with flat national rates.

CPT 87186

Antimicrobial Susceptibility Testing (MIC Method)

CPT 87186 is antimicrobial susceptibility testing using the minimum inhibitory concentration (MIC) method. This test determines which antibiotics will effectively kill bacteria identified in a culture. It generates an additional charge on top of the culture itself. Medicare pays approximately $8 to $12, but providers charge an average of $53.73. For simple infections like uncomplicated UTIs, empiric antibiotic treatment without susceptibility testing is often standard practice, meaning this $54 charge may not change your treatment.

Updated May 2026Source: CMS Clinical Lab Fee Schedule

CPT 87186 at a Glance

Medicare CLFS rate: ~$8 to $12
Average provider charge: $53.73
Markup: 4.5 to 6.7x over Medicare rate
Billed in addition to: Culture charge

Test type: Antibiotic sensitivity (MIC)
Beneficiaries (2023): 1.43 million
Fee schedule: Clinical Laboratory (CLFS)
Rate type: National (no geographic adjustment)

How Lab Pricing Works (Clinical Laboratory Fee Schedule)

CPT 87186 is priced under the Medicare Clinical Laboratory Fee Schedule (CLFS) at a single national rate. There is no geographic adjustment. This test is always billed in addition to the bacterial culture that identified the organism. So your total microbiology bill typically includes the culture (e.g., CPT 87088 for urine culture) plus the susceptibility testing (87186).

Metric	Value
Medicare CLFS Rate	~$8 to $12
Average Provider Charge	$53.73
Markup Ratio	4.5 to 6.7x
Pricing Method	National rate (CLFS), no geographic variation

Hidden add-on cost: Susceptibility testing is never ordered alone. It always appears alongside a culture charge. A typical urine culture with susceptibility testing generates two separate charges: the culture ($30 to $60) plus the susceptibility ($54). Together, that is $84 to $114 for what many patients think of as "a urine test." For uncomplicated UTIs with predictable bacteria, empiric treatment without culture is standard practice.

Lab tests are priced under the Clinical Laboratory Fee Schedule, not the Physician Fee Schedule. Medicare lab rates are set nationally and do not vary by geographic location.

What Does Antimicrobial Susceptibility Testing Measure?

After a bacterial culture grows and identifies the specific organism causing your infection, susceptibility testing exposes that bacteria to various antibiotics at different concentrations. The MIC (minimum inhibitory concentration) method determines the lowest concentration of each antibiotic that prevents bacterial growth.

What the Results Show

Sensitive (S): Antibiotic will likely work at standard doses
Intermediate (I): May work at higher doses
Resistant (R): Antibiotic will not work
MIC value in mcg/mL for each antibiotic tested

When It Is Most Valuable

Complicated or recurrent infections
Hospital-acquired infections (higher resistance)
When first-line antibiotics have failed
Immunocompromised patients
Infections with multi-drug resistant organisms

Timing matters: Susceptibility results take 24 to 48 hours after the culture grows (which itself takes 24 to 48 hours). So you may wait 2 to 4 days for results. For time-sensitive infections, doctors start empiric antibiotics immediately and adjust if susceptibility results show resistance. Ask your doctor: "For my infection, do we need to wait for susceptibility, or can we treat empirically?"

Where to Get Susceptibility Testing for Less

Unlike simple blood tests, susceptibility testing requires a bacterial culture to be grown first. This limits your options for price shopping. However, where the culture is performed matters:

Independent Reference Labs: $15 to $30

Large reference labs like Quest and LabCorp process millions of cultures and have automated susceptibility testing systems. Their charges are typically lower than hospital labs. If your doctor sends a culture, ask if it can go to an independent lab.

Ask Whether Susceptibility Testing Is Needed

For simple, uncomplicated UTIs in otherwise healthy women, current guidelines support empiric treatment with antibiotics (like nitrofurantoin or trimethoprim-sulfamethoxazole) without culture or susceptibility testing. This eliminates the $84 to $114 culture-plus-susceptibility charge entirely. Ask your doctor: "Is this a straightforward infection where we can treat empirically?"

Hospital Microbiology Labs: $40 to $80+

Hospital labs charge the most, with the national average at $53.73 for the susceptibility component alone. Combined with the culture, total microbiology charges can exceed $100 at hospital labs.

What Insured Patients Actually Pay for Susceptibility Testing

Insurance negotiated rates for lab tests are typically at or near Medicare CLFS rates. Your out-of-pocket cost depends on your deductible status:

Your Situation	What You Likely Pay	How It Works
Copay plan (deductible met or N/A)	$0	Many plans cover lab work at 100% after deductible
Coinsurance plan (deductible met)	$1.60 to $2.40	20% of negotiated rate ($8 to $12)
High-deductible plan (deductible NOT met)	$8 to $25	Full negotiated rate applied to your deductible
Medicare Part B	$0	Medicare covers clinical lab tests at 100% (no coinsurance)

Common Billing Problems with CPT 87186

Multiple susceptibility charges for different methods

Some labs bill both 87186 (MIC method) and 87184 (disk diffusion method) on the same organism. While this can be legitimate if both methods were truly performed, it is unusual to need both for the same isolate. If you see both codes on the same culture, ask why two different methods were necessary.

Susceptibility testing on cultures that showed no growth

Susceptibility testing can only be performed on bacteria that actually grew in culture. If your culture was reported as "no growth" or "normal flora," there should be no 87186 charge. If you see a susceptibility charge alongside a negative culture result, dispute it.

Routine culture and sensitivity for uncomplicated UTI

For simple, first-time UTIs in healthy women, guidelines support empiric treatment without culture. If your doctor ordered a full culture with susceptibility for a straightforward UTI and you were already started on antibiotics before results came back, the $84 to $114 combined charge may not have been necessary. This is a clinical judgment call, but worth discussing with your provider.

Frequently Asked Questions

How much does antimicrobial susceptibility testing cost?

Susceptibility testing by MIC method (CPT 87186) averages $53.73 per charge at hospitals. Medicare pays approximately $8 to $12. This is always billed in addition to the bacterial culture charge (another $30 to $60), so total microbiology bills for culture plus susceptibility often reach $84 to $114 or more.

Is susceptibility testing always necessary after a bacterial culture?

No. For simple infections where the bacteria and its resistance patterns are predictable (like uncomplicated UTIs), empiric antibiotic treatment is standard practice. Susceptibility testing is most important for complicated infections, hospital-acquired infections, recurrent infections, and situations where first-line antibiotics have failed.

Can CPT 87186 be billed multiple times on the same specimen?

CPT 87186 is typically billed once per isolate tested using the MIC method. If multiple organisms grew from your culture, you may see multiple susceptibility charges (one per organism). However, if only one organism grew and you see multiple 87186 charges, ask for clarification on what each charge represents.

What is the difference between CPT 87186 and CPT 87184?

CPT 87186 uses the MIC (minimum inhibitory concentration) method, which determines the exact antibiotic concentration needed to stop bacterial growth. CPT 87184 uses disk diffusion (Kirby-Bauer method), a simpler qualitative approach. Most modern labs use automated MIC systems, making 87186 more common. Seeing both codes on the same organism is unusual and worth questioning.

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