This page explains how UK guidance expects you to watch a medicines fridge or store: what to measure with, how often to read it, who the alarm has to reach and how often the instruments need calibrating. The one thing to remember is that a min/max thermometer tells you how far the temperature went but not for how long, so your monitoring has to be good enough to answer the question an excursion will ask.
Why it matters
Monitoring is only as good as the question it can answer
Most temperature problems are found later, when someone looks at a reading and has to decide whether the stock is still fit to give a patient. At that moment you need two facts: how far out of range it went, and for how long. A max/min thermometer gives you the first but not the second, which is why NHS SPS tells you to assume the excursion started just after the last reset unless you have evidence otherwise. Over a weekend that can mean about 72 hours, and stock a logger would have shown was fine gets thrown away.
The opposite failure is false reassurance. The RPS (2018, archived but not withdrawn) describes a vaccine fridge whose built-in display read normally while an independent thermometer showed 0 °C; every vaccine was destroyed. The MHRA's 2020 transport blog describes a temperature trail where the "lack of alarm triggering led to incorrect assurance that stock was within acceptable temperature range". Monitoring you cannot trust is, in practice, no monitoring at all.
What the rules say
Monitoring and alarms: law, guidance, then interpretation
For wholesalers the starting point is law. Regulation 43 of the Human Medicines Regulations 2012 makes compliance with the GDP guidelines a licence condition, enforced by the MHRA at inspection. EU GDP (2013/C 343/01) section 3.3 says alarms should alert staff to excursions from pre-defined storage conditions, be set appropriately and be regularly tested. It does not say how often to test, how long a delay may be, or who responds out of hours, so your procedures have to justify those.
In primary care the reference is Green Book chapter 3. In England it asks for current, maximum and minimum readings at least once each working day, at the same time, with each entry signed, and at least one max/min thermometer that runs independently of mains power alongside any built-in display. CQC restates this in GP mythbuster 17 and says that a data logger does not remove the daily manual reading. For care homes, CQC asks for at least once a day, which in a home open every day means weekends too.
NHS SPS adds the practical detail most sites work from. Its sensor guidance calls a min/max recorder the minimum and recommends at least one air sensor (early warning) and one load sensor in a buffered mock product (the medicine's likely temperature). Its alerts guidance suggests an alarm just inside the limit, such as 7.5 °C for an 8 °C maximum, a delay 'as short a period as practically possible', no permanent silencing, and networked SMS, email or telephone alerts as "the most robust means of alerting users" when nobody is in the building. SPS also asks for loggers compliant with BS EN 12830; what that standard asks of a recorder, and where it is law, is in our EN 12830 guide.
Calibration: how often, and to what standard
EU GDP 3.3 makes calibration of storage monitoring equipment risk-based: defined intervals based on a risk and reliability assessment, traceable to a national or international standard, with records kept. Transport is different. EU GDP 9.2 sets one of its few fixed figures: monitoring equipment in vehicles and containers is calibrated at least once a year.
UK sector guidance is firmer for storage. The Green Book asks for the independent max/min thermometer to be calibrated every year. SPS says sensors should be calibrated annually to ±0.5 °C by a UKAS-accredited service, with 2-point or 3-point calibration acceptable and 3-point, in SPS's reading, required in departments operating under an MHRA licence. The MHRA and EU GDP texts themselves are risk-based and set no number of points; the HPRA asks for at least three. WHO Annex 9 adds that calibration should show accuracy across the whole range the device is used over.
The MHRA GXP data integrity guidance says a simple thermometer with no configurable software or stored data 'may only require calibration'. A logger with software, configurable alarms or a dashboard needs validating too; see records and data integrity.
What good looks like
Every working day: read, record, reset, react
The Green Book's four Rs are the backbone of the daily routine. Read the current, maximum and minimum temperatures at the same time each day. Record them on a standard form and sign the entry. Reset the thermometer after each reading, because if nobody resets it every later reading shows the old maximum and an incident becomes very hard to investigate. React if the reading is outside +2 °C to +8 °C, and write down what you did.
SPS also asks for an independent daily check that the readings and resets were done, and the VMD makes the same point for vet practices: a logger does not replace a daily look to confirm the device works and no alert has fired. Know your alarm's threshold and delay before you need them; the UKHSA incident checklist asks how long the fridge was out of range before the alarm sounded.
- Labelled storage range
SPS's example: an alarm at 7.5 °C for an 8 °C maximum gives staff time to act before an excursion. Set your own thresholds in your procedure; our recommendation below is a starting point.
Every week and every year
Weekly, download and review any logger. The NHS England South West ICARS toolkit suggests doing it on the first morning after the weekend, before the first vaccine is given, with loggers set to 5-minute intervals so the length of any breach can be worked out. SPS also wants logger data reviewed for slow trends such as gradual drift, which a daily glance will not show.
Yearly, calibrate the sensors, keep the certificates and have the fridge serviced. Test alarms at their set points through the whole notification route, not just the local sounder. WHO model guidance (4.10.3) says "at least once every six months at the designated set points"; UK guidance says 'regularly', so set an interval and record each test; our recommended interval is below.
Worked example
Monday morning, the max reads 9.4 °C
This is an illustrative example. A GP practice is closed over the weekend. At 08:30 on Monday the practice nurse reads the vaccine fridge: current 5.1 °C, minimum 3.8 °C, maximum 9.4 °C. She records all three values and signs the entry before resetting, because resetting first would destroy the evidence.
The max/min reading cannot say when the rise happened or how long it lasted, so under the SPS approach she assumes it began just after Friday's reset. She labels the stock 'do not use' and quarantines it in the fridge. The fridge also has a logger, so she downloads it. The trace shows one rise above 8 °C, lasting 14 minutes, during Friday afternoon's delivery restock.
UKHSA says a one-off rise above 8 °C lasting under 20 minutes, for example during restocking, with the vaccines in their original packaging and stored correctly before the event, is unlikely to have breached the cold chain and needs no action beyond recording the cause. This is NHS clinical guidance; it does not apply to WDA or MIA holders. She records the reading, the logger evidence, the cause and her conclusion. Had the logger shown a longer excursion, she would follow the excursions process.
Where it's unclear
Where the sources disagree
Reading frequency differs by nation and setting, from once each working day in England to twice a day, seven days a week in WHO model guidance (once or twice daily, weekends and closed periods). CQC expects GP practices to keep the daily paper reading even with a logger, while SPS points to continuous monitoring with remote alerts (logger versus daily reading).
Only WHO sets an alarm test interval (alarm testing); calibration intervals and points vary (calibration); and probe placement differs between the MHRA's 2016 blog and EU GDP (probe placement, and see mapping). In each case, follow your sector's guidance, assess the risk to your stock, and record your reasoning.
Inspection findings
What MHRA inspectors have found
The MHRA GDP deficiency data for 2016 cites, as major deficiencies, a warehouse thermometer not calibrated across its operating range, an ambient thermometer installed so readings did not come from the calibrated probe, uncalibrated equipment used to monitor transport, and a fridge with ice build-up reading 0.6 °C with unrecorded changes to its control dial.
The 2016 GMP deficiency examples include alarm limits wider than the product storage range, twice-daily spot readings with no max/min data, and no acceptance criteria for external calibration of warehouse probes. These are examples published to support self-inspection, not new requirements; responsibility and inspection covers CQC and GPhC findings. Stability chambers and other GMP storage have their own rules and our recommended alarm limits and delays: see GMP storage, mapping and monitoring.
In summary
The short version
- Use at least one independent max/min thermometer, and consider a logger so you can tell how long an excursion lasted.
- Read, record and reset every working day (every day in a care home), and check that it was done.
- Set alarms just inside the limit with the shortest practical delay, and make sure an alert reaches a person out of hours.
- Test alarms at their set points, end to end, at an interval you have written down.
- Calibrate annually against a traceable standard, across the range you use, and keep the certificates.
- Download and review loggers weekly, looking for drift as well as excursions.
- Where sources differ, follow your sector's guidance, assess the risk and record your reasoning.