Which pharmacy batches will expire before you can sell them?

The batch expiring in 30 days may be the safest one on your shelf. If you have 60 units and sell three a day, you can sell that batch in 20 days. The surprise can be the batch behind it: it has a later expiry date, but part of its selling time belongs to the first batch.

To estimate pharmacy stock expiry risk, forecast how many units you can sell before each batch’s cutoff. Give the earliest eligible batch first claim on those sales. Then multiply the units likely to remain in each batch by what you paid for them.

Start with one product and one unit of measure

Take one item of the same strength, form and pack specification. Count the saleable units in each lot and record the batch number, acquisition cost per unit and last eligible selling date. Use your facility’s applicable cutoff if it falls before the labelled expiry. Leave quarantined, recalled or otherwise ineligible stock out of the saleable balance.

Use tablets throughout if you sell by the tablet, or packs throughout if you sell by the pack. Estimate demand from recent units actually sold or issued. If you sold 84 units over 28 days with stock available, your starting rate is three units per day. If stockouts, seasonality or a one-off order distorted that period, test a second rate.

Work through three batches on the same shelf

This fictional pharmacy expects to sell three units a day. All three lots are eligible today. There are no incoming deliveries, reservations or transfers. Costs are in the same local currency throughout.

Batch A — 30 days left. You have 60 units at 2.00 each. At three units a day, all 60 should sell by day 20. Units at risk: 0.

Batch B — 60 days left. You have 140 units at 2.50 each. Batch A takes the first 20 days of sales, leaving 40 days to sell Batch B. At three units a day, you expect to sell 120 of the 140. Units at risk: 20. Cost at risk: 50.

Batch C — 75 days left. You have 55 units at 3.00 each. After Batch B reaches its cutoff on day 60, you have 15 days to sell Batch C. You expect to sell 45 units. Units at risk: 10. Cost at risk: 30.

Buying decision: Across the three batches, 30 units may expire unsold, at a total acquisition cost of 80. Start with Batch B. It accounts for 50 of that exposure, even though Batch A expires first.

Batch A can sell all 60 units by day 20. That gives B the next 40 days before its cutoff, enough to sell 120 of its 140 units. After day 60, C has 15 days left and can sell 45 of its 55 units.

The forecast puts 30 units at risk, with an acquisition cost of 80: 20 × 2.50 from B and 10 × 3.00 from C. The batch with the earliest expiry contributes none of that exposure.

Use the same calculation on your stock

Sort eligible lots by earliest cutoff. This follows first-expiry, first-out (FEFO), which WHO describes as issuing eligible stock in expiry-date order regardless of when it arrived. For each batch, write down three figures:

Available demand = daily unit sales × days until this cutoff, minus sales already allocated to earlier batches. Use zero if the result is negative.

Expected sales = the smaller of available demand and units on hand in this batch.

Cost at risk = (units on hand − expected sales) × batch acquisition cost per unit.

A common buying mistake is to give B all 180 sales expected by day 60. Sixty of those sales already belong to A. Counting them twice makes B look safe and can persuade you to order more of a product you already have too much of.

Decide what to do before the next order

Start with B. It has 50 in cost exposed, and its cutoff comes before C’s. Check whether your supplier still accepts returns, or whether another branch can use some of those 20 units in time. For a transfer, check the receiving branch’s own batches, demand and time left after transport. Moving stock only helps if that branch can actually use it.

Now test a slower week. At two units a day, A still sells its 60 units. B sells 60 and C sells 30. The exposure rises to 275: 80 units of B at 2.50 plus 25 units of C at 3.00. Treat this as a forecast for a buying decision. Record an actual write-off separately under your facility’s procedures.

A five-minute check before you reorder

Pick one product with at least two lots. Count it on the shelf, check the dates against the stock record and run the calculation at your usual daily rate. Circle the batch with the most money at risk. Write one action beside it, give it an owner and set a review date before the next supplier order or return deadline.

If you use PharmaSys, start with the batch quantities, expiry dates and purchase costs you already record. The useful number to take into your next buying decision is the cost of the units you expect to have left.

References

World Health Organization. Standard operating procedures, section 7, First expiry, first out. https://iris.who.int/bitstream/handle/10665/360835/9789240049581-eng.pdf

Médecins Sans Frontières. Organization and management of a pharmacy, stock management. https://medicalguidelines.msf.org/en/viewport/EssDr/english/organization-and-management-of-a-pharmacy-16688159.html