HCPCS Code J1645: Dalteparin sodium (Fragmin) billing guide

Key takeaways

HCPCS Code J1645 describes an injection of dalteparin sodium (Fragmin), billed per 2500 IU of the drug administered.

Bill one unit of J1645 per 2500 IU ordered, so a 5000 IU dose is 2 units and 10,000 IU is 4 units.

Medicare Part B reimburses J1645 at ASP+6%, and the NDC on the claim carries the F2 unit of measure qualifier.

Fragmin is approved for thrombosis prophylaxis and extended treatment, not for the acute treatment of VTE.

A single-dose container needs modifier JZ when no drug is discarded, or JW to report the discarded amount.

HCPCS Code J1645 is the Level II code for an injection of dalteparin sodium, billed per 2500 international units. Each unit covers 2500 IU, so a 10,000 IU dose of Fragmin bills as four units rather than one.

This guide covers the code details, the dose-to-unit calculation, and the ICD-10 codes that support medical necessity. It also covers Part B reimbursement, place of service rules, and the modifiers a drug line needs.

HCPCS Code J1645: definition and code details

Dalteparin sodium is sold under the brand name Fragmin and belongs to the low molecular weight heparin (LMWH) anticoagulant class. J1645 sits in the J-code series, which CMS maintains for drugs and biologicals given by injection. Oral drug products are reported under a different code family.

The table below summarizes the core attributes of HCPCS Code J1645 as maintained by CMS.

Drug overview: dalteparin sodium (Fragmin)

Dalteparin sodium is a low molecular weight heparin derived from porcine intestinal mucosa. It works by inhibiting Factor Xa and, to a lesser extent, thrombin, preventing the clot formation that causes deep vein thrombosis and pulmonary embolism. Fragmin (the brand name manufactured by Pfizer) is available in single-dose prefilled syringes and multi-dose vials, which affects NDC reporting requirements on claims.

The FDA has approved dalteparin for the indications below, and the label draws a firm line between prophylaxis and treatment.

• DVT prophylaxis in abdominal surgery patients at risk for thromboembolic complications
• DVT prophylaxis in hip replacement surgery patients
• DVT prophylaxis in acutely ill medical patients with severely restricted mobility
• Extended treatment of symptomatic VTE in cancer patients, to reduce recurrence over a longer course
• Extended treatment of symptomatic VTE in pediatric patients aged 1 month and older, to reduce recurrence

Fragmin’s label states plainly that it is not indicated for the acute treatment of VTE. That wording decides how a J1645 claim has to read. A line built around an acute DVT or PE treatment narrative does not match an approved use, however well the dose is documented.

Off-label use of dalteparin does not generate a covered claim on its own. The ICD-10 code on the claim must correspond to an FDA-approved or payer-recognized indication. Cancer-associated thrombosis needs careful pairing, because the malignancy code and the thrombosis code both have to appear.

J1645 billing units: how to calculate doses

Each unit of HCPCS Code J1645 represents 2500 IU of dalteparin sodium. The units billed must match the dose ordered and administered, not the amount held in the vial. Round to the nearest whole unit, since CMS does not permit partial units on a J1645 line.

The table below shows the unit calculation for the most common dalteparin doses.

Wastage rule: when a single-dose container holds more drug than the dose ordered, Medicare pays for the discarded portion if it cannot be salvaged. Report the administered amount on one line and the discarded amount on a second line with modifier JW.

When a single-dose container yields no waste, append modifier JZ instead to attest to that. CMS required JZ reporting from July 1, 2023, and began rejecting claims without JW or JZ as unprocessable on October 1, 2023. A missing modifier is enough on its own to stop the line. Document the dose ordered, the dose given, and any discarded amount in the patient record.

Confirm your Medicare Administrative Contractor’s wastage policy before you rely on it, since the rules vary by setting and container type.

ICD-10 diagnosis codes that support medical necessity

Every J1645 claim requires a supporting ICD-10-CM diagnosis code that establishes medical necessity. The diagnosis must reflect the clinical indication documented in the patient record. The table below lists the primary ICD-10 codes paired with HCPCS Code J1645 claims across DVT, pulmonary embolism, and cancer-associated thrombosis indications.

Every entry in the clinical context column assumes prophylaxis or extended therapy. The label rules out acute VTE treatment, so a diagnosis code cannot make an acute treatment claim payable on its own.

For cancer-associated thrombosis claims, add the patient’s specific malignancy code to the DVT or VTE code. Examples include C18.9 for colon cancer and C50.911 for breast cancer. A bare Z85 personal history code will not support medical necessity by itself. Confirm code validity against the CDC/NCHS ICD-10-CM tool for the applicable fiscal year.

Medicare Part B reimbursement and NDC reporting

Medicare Part B reimburses HCPCS Code J1645 under the buy-and-bill model at the average sales price (ASP) plus 6 percent. CMS recalculates ASP every quarter from the net selling prices manufacturers report. The 6 percent add-on offsets the cost of buying, storing, and administering the drug.

Because ASP is refreshed quarterly, the per-unit payment for J1645 changes four times a year. Check the current figure in the CMS ASP drug pricing files before projecting revenue, since the Physician Fee Schedule lookup does not carry drug rates. Three billing requirements apply to every Part B J1645 claim.

• NDC reporting: report the National Drug Code on every Part B drug claim, as required by the Medicare Claims Processing Manual (Chapter 17). The NDC must match the product administered. Dalteparin is dosed in international units, so the unit of measure qualifier is F2, not UN. A Fragmin 5000 IU prefilled syringe carries a different NDC than a 10,000 IU vial.
• Units billed: bill units on the dose administered, calculated per 2500 IU. Do not bill the whole container when part of it went unused, unless the wastage rule and its modifiers apply.
• Place of service: the payment rate for J1645 can differ by place of service. Office claims under POS 11 typically pay more than outpatient hospital claims under POS 22, which fall under OPPS.

Build the check into the document the biller works from. The charge record for a J1645 dose should carry the code, the units, the NDC, the dose given, the route, and the diagnosis. Reconciling that record against the remittance advice by denial reason code shows which field the payer keeps rejecting.

Place of service and revenue codes

The place of service (POS) code on a J1645 claim decides which payment system applies. Physician-administered claims use the CMS-1500 form with a POS code. Institutional outpatient claims use UB-04 with a revenue code. The table below summarizes the relevant settings for dalteparin administration.

Home health agencies have no place of service code of their own, so no row above covers them. They submit institutional claims on a UB-04, and drugs other than covered osteoporosis injections sit outside home health consolidated billing. Check the patient’s episode status before you bill J1645 under a home health plan of care.

Coverage narrows sharply once the patient injects Fragmin at home. Part B then turns on whether the dose qualifies for an exception to the self-administered drug exclusion.

Dalteparin is generally not covered as a self-administered drug for home use under Part B. An exception needs a qualifying condition that prevents self-injection. Verify your Medicare Administrative Contractor’s Local Coverage Determination before you bill J1645 in a home setting.

J1645 vs J1650: dalteparin vs enoxaparin

J1645 and J1650 are the two most frequently confused low molecular weight heparin codes. Both describe injectable anticoagulants in the same drug class, but they cover different drugs and use different per-unit structures. Submitting J1650 when the patient received dalteparin (or vice versa) generates an automatic payer rejection. Use this comparison table to distinguish the two codes before submitting.

The unit measurement is the most common source of error when switching between J1645 and J1650. Dalteparin is measured in IU. Enoxaparin is measured in mg. Mixing up the denominator makes the unit count wrong even when the coder picks the right drug. Verify the drug name on the administration record first, then confirm the descriptor in the AAPC HCPCS code lookup.

Common billing errors and compliance tips

The Office of Inspector General treats drug injection billing as a high-risk area for improper payments. Most J1645 errors are procedural rather than deliberate, but a repeated pattern draws a payer audit. Each one shows up in a single claim line, so it helps to see what a compliant line carries.

The errors below account for most J1645 denials and recoupments.

• Unit miscalculation: billing 1 unit for a 10,000 IU dose instead of 4 units is the most common error. Build a calculation prompt into your billing workflow using the dose-to-unit table above.
• Missing or incorrect NDC: omitting the NDC from a Part B drug claim produces an automatic line-level denial. The NDC must reflect the package size administered, with the F2 qualifier for international units.
• Missing waste modifier: a single-dose container line without JW or JZ denies on its own. Add JZ when no drug is discarded, and JW on a separate line when some is.
• ICD-10 mismatch: a J1645 line built on an acute VTE treatment narrative fails medical necessity review, because the label does not cover that use. The diagnosis and the notes have to support prophylaxis or extended treatment.
• Wrong place of service: an infusion suite dose belongs under POS 22, not POS 11. Billing the office code creates a payment differential and a recoupment risk.
• Billing for non-covered home administration: Part B does not routinely cover self-administered dalteparin at home. A J1645 line with POS 12 and no qualifying exception is a common audit trigger.
• Prior authorization omission: commercial payers increasingly require prior authorization for LMWH therapy beyond a set number of days. Check payer policy before you submit past the initial course.

Pre-submission auditing is what keeps these off the remittance. Review the dose ordered in the chart, calculate the units, and confirm the NDC. Then match the diagnosis to the documented indication and check the modifier and the place of service.

It is worth learning which denial codes your payers return most often on drug lines, since each one points at a specific field. A clean claim on the first pass avoids the rework cycle that delays payment on a drug the practice has already bought.

How Pabau keeps dose and claim data together

A Fragmin dose is usually recorded in one system and billed from another. The dose ordered sits in the clinical note, the NDC and lot number sit on the medication record, and the biller retypes both. Every retype is a chance to bill one unit instead of four.

Pabau, practice management software for medical and aesthetic practices, holds the drug, the dose, the diagnosis, and the treatment note on one patient record. Its claims management software pulls that stored data into a pre-filled claim, then submits and tracks it. Pabau does not pick the code or the diagnosis for you, so a coder still owns the J1645 line.

The outcome is a shorter path between what the nurse recorded and what the payer receives. Fewer hand-copied fields mean fewer of the transcription errors that put a J1645 line on the denial report.

Keep drug doses and claim data together

Pabau keeps the dose, the units, and the diagnosis on one patient record. It pulls that stored data into a pre-filled claim you can submit and track.

Book a demo

Conclusion

A J1645 line pays when it agrees with the chart on four points. Those are the units, the NDC and its F2 qualifier, the waste modifier, and a diagnosis that matches an approved use.

That last point is where this code parts company with the rest of the LMWH family. Fragmin’s label rules out acute VTE treatment, so no amount of documentation makes an acute treatment claim payable. Write the order and the note around prophylaxis or extended treatment, and let the diagnosis follow.

If your team bills J-codes regularly, the cheapest fix is catching these fields before the claim leaves. Book a demo to see how Pabau keeps drug doses, diagnoses, and claim data on one record.

Continue your research

Need a deeper guide to medical claims submission? Medical billing workflows explained walks through the full claims lifecycle from charge capture to remittance.

Struggling with denied claims on drug injections? Denial management in healthcare covers root cause analysis and appeal strategies for common denial patterns.

Want to understand how electronic claims are filed? 837 electronic claim file explains the EDI format used for Part B drug claims, including J-code submissions.

Frequently asked questions