Maintenance and calibration frequency for laboratory equipment
A starting interval table for 21 categories of lab instrument — preventive maintenance and calibration — plus how to set an interval you can defend to an assessor.
Last reviewed August 11, 2026
Who decides the interval
This is the part labs most often get wrong, so it is worth saying first: no accreditation body publishes the interval for your instrument. ISO 15189:2022 clause 6.4.4 requires the laboratory to have a maintenance programme and clause 6.5 requires calibration where measurement affects the result — both put the interval in your hands. An assessor is not checking your number against a master list. They are checking three things:
- You defined an interval for every instrument.
- You can say where the interval came from.
- The records show you actually kept to it.
The third one is where most findings are raised, and it is the cheapest to fix.
Where a defensible interval comes from
In roughly this order of authority:
- The manufacturer's service manual. If the manual says the probe wash cycle is monthly, monthly is your interval and the justification writes itself.
- The measurement's own tolerance. An electrolyte analyser drifts faster than a water bath, so it is calibrated more often.
- Your own history with that instrument. After a year you know which analyser fails between services; that evidence justifies tightening the interval, and a clean run justifies relaxing it.
- Workload. An instrument at 400 samples a day is not on the same clock as the identical instrument doing 40.
Starting intervals by instrument category
These are the defaults AssetLab applies when a lab registers an instrument, so a new register is never left with blank schedules. They are a reasonable opening position for a mid-sized diagnostic lab — not a standard, and not a substitute for the manual.
| Instrument category | Preventive maintenance | Calibration | Typical criticality |
|---|---|---|---|
| Biochemistry analyzer | 30 days | 6 months | critical |
| Haematology analyzer | 30 days | 6 months | critical |
| Immunoassay analyzer | 30 days | 6 months | critical |
| Coagulation analyzer | 3 months | 6 months | major |
| Urine analyzer | 3 months | 1 year | minor |
| Electrolyte / ABG analyzer | 30 days | 3 months | critical |
| Microbiology system | 3 months | 6 months | critical |
| Molecular / PCR | 3 months | 1 year | critical |
| Microscope | 6 months | — | major |
| Centrifuge | 3 months | 1 year | major |
| Refrigerator / freezer | 30 days | 6 months | critical |
| Incubator | 3 months | 6 months | major |
| Autoclave | 30 days | 6 months | critical |
| Water bath | 6 months | 1 year | minor |
| Pipette | 6 months | 1 year | major |
| Weighing balance | 6 months | 1 year | major |
| Thermometer / data logger | — | 1 year | major |
| Hot air oven | 3 months | 6 months | major |
| Laminar air flow | 3 months | 6 months | critical |
| UPS / power | 3 months | — | critical |
A dash means the category is not normally calibrated or not normally on a fixed service cycle — a microscope is maintained but has nothing to calibrate against a reference; a data logger is calibrated but has no service interval of its own.
Why criticality belongs in the same decision
Interval and criticality are usually set together, because criticality is what decides how much a missed date costs you. A critical instrument is one where failure stops reporting or puts a released result in doubt — the main analysers, the electrolyte analyser, the autoclave, the vaccine and reagent refrigerator, the UPS holding them all up. For those, the useful question is not only how often to service, but how quickly you can be back up, which is a contract question rather than a schedule one.
A minor instrument on a lengthened interval and a critical one on a tightened interval is a defensible programme. The same interval applied to everything, because that was the default nobody changed, is the pattern that draws questions.
The interval is worth nothing without the record
A schedule proves intent. Assessors look for evidence, and the two are not the same document. For each completed service you want the date, who did it, what was done, what was found, and whether the instrument was fit to return to use. For each calibration you want the certificate number, the reference standard it was traceable to, the result, and the next due date.
The distinction matters more than it sounds. A planned date sitting in a schedule is not evidence that anything happened, and a register that prints the two in the same typeface is one an assessor cannot read safely. That is why AssetLab prints a planned date and a recorded date differently, and prints “Not recorded” rather than inventing something plausible.
Common questions
Does ISO 15189 specify how often lab equipment must be calibrated?
No. ISO 15189:2022 and the national schemes built on it require the laboratory to define calibration and maintenance intervals and to be able to justify them. They do not publish a table of intervals. An assessor checks that you set an interval, wrote down why, and then actually kept to it.
What is a reasonable starting interval for a biochemistry analyser?
Most labs start with preventive maintenance every 30 days and calibration every 180 days, then adjust from the manufacturer's manual and their own breakdown history. The manufacturer's stated interval takes precedence over any general table.
Can we lengthen an interval to reduce cost?
Yes, if you can defend it with evidence. Extending an interval is a decision that needs a reason recorded at the time — typically a run of clean calibrations, stable QC and no related breakdowns. Extending it silently, with no record, is what turns into a finding.
Which equipment needs calibration at all?
Anything whose measured value affects a reported result, plus anything that has to hold a condition within limits — analysers, pipettes, balances, thermometers, centrifuge speed, incubator and refrigerator temperature, autoclave pressure and temperature. A microscope or a UPS is maintained but not calibrated.