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Short answer
A par level in pharmacy is a preset stock quantity for a medication storage location, most often an automated dispensing cabinet (ADC). Many pharmacies set two numbers: a minimum par, which triggers a refill request, and a maximum par, the quantity meant to last until the next refill (Walczyk et al., Hospital Pharmacy, 2024). This page covers inventory control only, not dosing or clinical decisions.
Definition and scope
What is par level in pharmacy?
“Par” stands for periodic automatic replenishment. In a hospital pharmacy it describes how much of an item a location should hold and when it should be restocked. The peer-reviewed definition used here comes from a 2024 comparison of inventory models in ADCs: inventory levels “are usually determined by setting minimum and maximum periodic automatic replenishment (par) levels.”
Another study of ADC optimization describes par inventory levels as the “desired on-hand quantities of medications” and also refers to par reorder quantities (McCarthy and Ferker, American Journal of Health-System Pharmacy, 2016). So the cited sources use the word for the target quantity, the reorder trigger, or both.
This page is about drug stock in ADCs. For the general arithmetic of par in non-drug clinical supplies, such as supply carts and lab benches, see the CASRAI term par level (inventory).
How par levels work in an automated dispensing cabinet
What is a par level in a pharmacy cabinet?
In the ADC study, the minimum par is the point at which the cabinet asks for a refill: when unit doses are exhausted down to that level, the cabinet generates a refill request. The maximum par is “a quantity based on predicted need to ensure sufficient quantity exists to last between refills.” (Walczyk et al., 2024).
At the study hospital the levels were calculated from usage and then entered by hand through the cabinet’s software console. The authors note that, before the study, inventory levels there were “set by pharmacists’ experience and discretion, thus may vary widely.”
Minimum vs maximum par: what each source says
What is the par level in a pharmacy, minimum or maximum?
Both, depending on the source. The table keeps each statement attached to the document that makes it.
| Item | What the source states | Source |
|---|---|---|
| Minimum par | The level at which an ADC generates a request to be refilled as unit doses are exhausted. | Walczyk et al., 2024 |
| Maximum par | A quantity based on predicted need so that stock lasts between refills. | Walczyk et al., 2024 |
| Par inventory level | The desired on-hand quantity of a medication; par reorder quantities are adjusted alongside it. | McCarthy and Ferker, 2016 |
| Counting-friendly quantities | Par levels should be kept to quantities that facilitate ease of counting, to increase inventory accuracy. | ASHP Guidelines on the Safe Use of ADCs, 2022 |
| Usage-based review | The maintenance checklist lists optimal par levels based on usage and stock-out analysis; storage practices should be reviewed against prescribing patterns, utilization and unit needs. | ASHP Guidelines, 2022 |
| Floor of 3 | At one study site, a calculated minimum par under 3 was set to 3. This is that site’s rule, not a general standard. | Walczyk et al., 2024 |
Where it matters for labs, clinics and supply decisions
Why par levels affect stockouts
At a large hospital that adjusted par levels, expanded common stock and removed rarely prescribed medications from its ADCs, the weekly stockout percentage fell from 3.2% before optimization to 0.5% eight months after. The authors also estimated $2,728 a year in technician labor saved and $19,660 in avoided expiration cost (McCarthy and Ferker, 2016). These are single-site results from a project that combined several changes, so they do not isolate the effect of par levels alone. For how a stockout is defined and measured, see stockout.
Related inventory ideas
Par-based replenishment is one of several replenishment signals. Kanban inventory uses a visible trigger in a similar way, and fill rate measures how often requested items are supplied. The ASHP guideline also links stock choices to diversion detection: removing infrequently used controlled substances from a cabinet shortens the inventory time and reduces delay in noticing diversion. See the CASRAI guide on controlled substance diversion prevention programs.
Common misunderstandings
- Par is not one fixed national number. The sources describe levels set locally from usage, and the study hospital reports they varied with individual pharmacists’ judgment.
- The ASHP guideline does not give a calculation method. It sets expectations (counting-friendly quantities, usage-based levels, routine review, stock-out analysis), not a formula.
- Par is not used the same way in every source. McCarthy and Ferker use par for the desired on-hand quantity, while Walczyk et al. split it into a minimum (the refill trigger) and a maximum (the quantity meant to last between refills); check which meaning a document uses.
- A study-site rule is not a standard. The minimum of 3 comes from one hospital’s method.
FAQ
What is a par level in pharmacy?
A preset stock quantity for a storage location such as an ADC, usually expressed as a minimum that triggers a refill request and a maximum that should last until the next refill.
What is the par level in a pharmacy for a given drug?
It is set locally by the pharmacy from its own usage, and ASHP’s guideline names usage-based levels without prescribing a method. This page does not list quantities for any medication.
What does PAR stand for?
Periodic automatic replenishment, as used in the 2024 Hospital Pharmacy study.
Is minimum par or maximum par the “par level”?
The cited sources differ. The peer-reviewed definition above uses both: minimum par triggers a refill and maximum par is the quantity meant to cover the gap between refills.
Sources
- Walczyk T, Hill JD, Gill C, et al. A Comparison of Inventory Management Models in Automated Dispensing Cabinets at a Large Academic Medical Center. Hospital Pharmacy, 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11097941 (date checked: 2026-10-31).
- McCarthy BC Jr, Ferker M. Implementation and optimization of automated dispensing cabinet technology. American Journal of Health-System Pharmacy 2016;73(19):1531-6. https://pubmed.ncbi.nlm.nih.gov/27646814/ (abstract; date checked: 2026-10-31).
- Cello R, Conley M, Cooley T, et al. ASHP Guidelines on the Safe Use of Automated Dispensing Cabinets. American Journal of Health-System Pharmacy 2022;79(1):e71-e82. https://academic.oup.com/ajhp/article/79/1/e71/6371096 (date checked: 2026-10-31).
