Bariatric surgery programs lose $50,000 to $150,000 annually to preventable billing errors — incomplete prior auth documentation, BMI not documented at the right interval, psychological clearance that doesn't meet payer-specific language requirements. The procedures themselves are clean and well-defined. The billing complexity is almost entirely on the front end.
The most common bariatric procedures each have their own CPT code, and choosing the right one isn't optional — wrong code selection is the single largest source of bariatric surgery payment delays, separate from the medical necessity denials. Here's the core procedure code set for 2026:
| Procedure | CPT Code | Approach | Avg. Medicare Rate |
|---|---|---|---|
| Sleeve gastrectomy | 43775 | Laparoscopic | $1,890 |
| Roux-en-Y gastric bypass | 43644 | Laparoscopic | $2,340 |
| Open Roux-en-Y gastric bypass | 43846 | Open | $2,100 |
| Adjustable gastric band | 43770 | Laparoscopic | $1,530 |
| Gastric band removal | 43773 | Laparoscopic | $1,210 |
| Gastric band removal + replacement | 43774 | Laparoscopic | $1,680 |
| Revision of gastric bypass | 43848 | Open | $2,450 |
| Conversion sleeve to bypass | 43775 + 43644 | Laparoscopic | Payer-specific |
Conversion procedures — converting a sleeve gastrectomy to gastric bypass — require careful code selection. Some payers want two separate codes; others have a single conversion code. The operative report must clearly state the conversion rather than treating it as a new primary procedure, or you'll face bundling denials.
The BMI requirements for bariatric surgery coverage are widely known: BMI ≥ 40, or BMI ≥ 35 with a qualifying comorbidity. What practices get wrong is the documentation window and specificity.
For Medicare, the BMI must be documented as a measured clinical value — not self-reported — within 12 months of the surgery date. Payers want to see a chart note that shows the actual measurement date, the calculated BMI, and the patient's weight and height at that visit. A BMI referenced in a referral letter from 14 months ago won't satisfy this requirement.
Qualifying comorbidities that allow BMI ≥ 35 coverage include:
The comorbidity documentation needs to show it's actively treated, not incidentally noted. A diabetes diagnosis on the problem list with no A1C measurements or medication record won't carry the authorization. The payer wants evidence the comorbidity is real and ongoing.
Most payers — and Medicare through its NCD 100.1 — require documented evidence that the patient has tried and failed non-surgical weight loss interventions before bariatric surgery becomes covered. The standard window is 6 months of supervised diet program participation, though some commercial payers stretch this to 12 months.
The supervised diet program requirement is where many practices lose authorization. The payer's definition of "supervised" is specific: a physician-directed program with documented monthly visits, dietary counseling records, and weight trend documentation at each visit. A patient who followed a commercial diet program on their own — even Weight Watchers or Noom — doesn't satisfy this requirement for most payers.
The psychological evaluation isn't a rubber stamp — payers read it, and a vague or incomplete evaluation triggers requests for additional information that can delay authorization by 4 to 8 weeks. The evaluation needs to address specific questions that the payer's clinical reviewers are looking for.
A complete bariatric psychology evaluation covers:
That last point is critical. A psychological evaluation that summarizes the patient's history but doesn't include a clear candidacy recommendation often gets kicked back by payer reviewers. The evaluation should end with a specific statement — something like "Patient is cleared for bariatric surgery without psychiatric contraindication" — not a list of observations and a neutral closing.
Denial rates in bariatric surgery run 15% to 25% on first submission for commercial payers, which is higher than most surgical specialties. The breakdown is predictable.
Medical necessity denials (40% of all denials): Usually tied to incomplete documentation of the BMI window, missing supervised diet records, or the psychological evaluation not meeting payer-specific language requirements. These are appellable with the right documentation — and win rate on bariatric medical necessity appeals is 60% to 70% when the documentation gap is filled correctly.
Authorization errors (25% of denials): The procedure performed didn't match the procedure authorized. A common scenario: auth was obtained for laparoscopic sleeve gastrectomy (43775) and the surgeon converted intraoperatively to gastric bypass (43644). The claim for 43644 comes back denied. The fix is a concurrent authorization request that covers both codes when conversion is a clinical possibility.
Exclusion denials (20% of denials): Some employer-sponsored plans exclude bariatric surgery entirely as a covered benefit. These are non-appellable — the plan simply doesn't cover it. But practices that verify benefits before scheduling consistently catch these upfront rather than discovering them post-surgery.
OIG has examined bariatric surgery billing repeatedly, with particular focus on two patterns: (1) billing for procedures in patients who didn't meet medical necessity criteria, and (2) upcoding — billing for gastric bypass when sleeve gastrectomy was performed, because bypass has a higher reimbursement rate.
RAC auditors targeting bariatric surgery typically pull 36 months of claims and look for cases where the medical record doesn't support the CPT code billed. If an audit finds a 20% error rate across a sample of 50 cases, the statistical extrapolation can project that rate across thousands of claims — resulting in demands well beyond the sampled amount. For a program doing 200 surgeries per year at an average Medicare rate of $2,000, a 20% extrapolated error rate generates a $160,000 recoupment demand on three years of claims.
The programs that hold up under audit have one thing in common: a documented clinical pathway that produces a consistent paper trail for every case. BMI measurement on a specific date in the chart. Six months of supervised diet visits with notes. Psych evaluation with a clear candidacy statement. Auth in the file before the procedure date. That's it. The complexity is in building the workflow, not in understanding the rules.
The billing gaps most practices don't catch until they show up as denials. Get the checklist — free, no spam.
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We audit bariatric surgery claims for authorization gaps, BMI documentation failures, and denial patterns — then fix the workflow so they don't happen again.
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