Where does infusion drug inventory go missing? Measuring shrink

Drug shrink is the gap between what your records say should be on the shelf and what's actually there. To find it, run one count per drug each month. Start with what you had and add what you received. Subtract what you gave, documented as waste, returned, and threw away for expiry or damage. Then compare that to a physical count. The leftover is unexplained loss. At infusion drug prices, a few missing units a month on one drug can cost more than a year of supplies.

I build reporting for infusion providers that lines up purchases, administrations, waste, and counts for every drug, so owners can see where units disappear. To see how inventory loss compares with your other leaks, use the infusion revenue leakage calculator. More on this work is on the infusion analytics page.

Key takeaways

• Shrink is what's left after every known movement is counted. It's not the same as waste, expiry, or excursion loss, which you can explain.
• One formula, per drug, per month: opening count plus received, minus administered, waste, returns, and expired or damaged, gives what should be on the shelf. Compare it with the physical count.
• Count in billing units or vials, never both. Mixing them is the most common reason a count looks wrong when nothing is missing.
• Check record gaps first: undocumented waste, patient-specific drug mixed with your stock, transfers between sites, and doses given but not recorded.
• Rank by dollars, not units. One missing vial of an expensive drug outweighs a box of cheaper ones.

Quick answers

• Count weekly: the short list of drugs that make up most of your drug spend.
• Count monthly: every other buy-and-bill drug.
• Count separately: patient-specific and free-drug-program stock, never in your own count.
• When in the day: at the same time each day, after the last administration is recorded.
• Where to look first: undocumented waste, then a mix-up between vials and billing units.

What counts as inventory shrink?

Shrink is the loss you can't explain. Every other movement of a drug has a record: you bought it, gave it, wasted part of a vial, sent it back, or threw it out because it expired or was damaged. When the shelf has less than those records add up to, the difference is shrink.

Keeping known losses separate matters because each has its own fix. Excursion losses point to storage, covered in how much temperature excursions cost. Waste from single-dose vials is billable for Medicare with the JW modifier, covered in the JW and JZ modifier guide. Shrink is what's left, and it usually means a record is missing somewhere.

How do you calculate shrink?

Use one formula per drug, per site, per month:

Expected on hand = opening count + received − administered − documented waste − returned − expired or damaged

Unexplained loss = expected on hand − physical count

Shrink rate = unexplained loss ÷ (opening count + received)

Here is one month at one site. All numbers are synthetic: replace them with your own. Units are billing units for each drug.

Drug A's shrink rate is 20 ÷ (400 + 1,200) = 1.25%. Drug C's is 4 ÷ (30 + 60) = 4.4%. Drug C has fewer missing units but costs more than three times as much, which is why the report ranks by dollars. The buy-and-bill margin calculator shows how much margin one dose of each drug carries, so you can see what a missing unit wipes out.

What if the count is higher than expected?

A negative gap means the shelf has more than your records say. That's not good news. It usually means a receipt was recorded twice, an administration was recorded that didn't happen, or a white-bagged dose was counted as your stock. Investigate it the same way. The white-bagging revenue impact guide explains how payer-mandated pharmacy shipments change what sits on your shelf.

Where does inventory usually go missing?

Most causes are gaps in records, so check those before assuming anything worse. The common ones, and where to look:

For groups with several sites, the multi-site KPI rollup guide shows how to report transfers so the group total still balances.

The "dose given, not recorded" cause is also a billing problem: if the administration isn't recorded, the visit may never be billed. That's one of the ten leaks in where infusion centers lose revenue between order and deposit.

How often should you count?

Count your most expensive drugs more often than the rest. A common approach:

• Weekly for the drugs that make up most of your drug spend. Usually that's a short list.
• Monthly for everything else that's buy-and-bill.
• Separately for patient-specific and free-drug-program stock, which should never be in your own count at all. The white-bagging waste calculator estimates what unused shipments of that stock cost you.

Count at the same point in the day, after the last administration is recorded, so the counts and the records describe the same moment.

Where do the numbers come from?

Each input lives in a different place, which is why shrink is rarely measured.

• Opening and physical counts: your count sheets or inventory system.
• Received: purchase invoices or your distributor's shipment records.
• Administered and waste: your infusion EHR's administration records.
• Returns and expired: return authorizations and your disposal log.

If you run WeInfuse, inventory on hand and lot details come from its inventory reporting. How to report WeInfuse inventory on hand by location and drug explains how to total it without double counting lots, and WeInfuse reporting help covers building the monthly count.

Keep in mind that drug used at visits isn't the same as approved supply or treatments remaining, as this explainer on the three inventory numbers covers. WeInfuse is a trademark of its owner; Greyfield Data is independent.

When these records sit in four systems, a single infusion data warehouse lines them up so the count runs itself.

This post is educational. Follow your state's rules and your own policies on inventory, disposal, and reporting suspected diversion.

What to do next

Pick your five most expensive drugs and run the count above for last month at one site. If a gap shows up, check the causes in the table in order, starting with undocumented waste and unit mix-ups.

The purchased versus billed report in the 12 weekly reports guide keeps the same check on a weekly cadence. The infusion analytics resource hub links every related guide. If you'd like the count built from your purchase, administration, and inventory records so it runs every month for every site, book a call with me.

Frequently asked questions