The answer to your question is yes, a medical company could calibrate their own equipment. In some cases, for example, an organization could have its own ISO 17025 accredited calibration laboratory that serves a number of manufacturing locations. Depending on the company, sector and the intended use of the instrument or device, there could be a number of ISO and other standards that would have to be complied with. There would be specific regulatory requirements that a medical instrument company would have to meet before they could sell their instruments. The crucial issue is that, if any company wished to calibrate their own equipment, they would have to provide a calibration that is suitably traceable to national or international references, as well as estimate and report the uncertainty of the calibration report. If the company did not have ISO 17025 accreditation for testing, they may need to obtain ISO 17025 accreditation for at least the calibration activity. If the company did have ISO 17025 accreditation for testing, then the quality management requirements related to calibration and traceability of the instruments in question would need to be met. Either way, the calibration must be performed by qualified competent personnel and a number of mandatory documents and records would be required, including:
Equipment and Calibration Procedure (Clauses 6.4.3 & 6.5)
Test and Calibration Method Procedure (Clauses 7.2.1 & 7.2.2)
Handling of Laboratory Test or Calibration Items Procedure (Clause 7.4)
Calibration Report and Certificate Requirements Procedure (Clauses 7.8.2 and 7.8.4, applicable to calibration laboratories that write calibration certificates)
Calibrated Equipment Record (Clause 6.4.13a)
Calibration Record (Clause 6.4.13e)
The following article could be of interest, where these documents are listed, along with others:
Question - In relation to recalibration or our own equipment What information would you look for on the calibration certificate to determine the equipment needs to be recheck and why?
I assume you are referring to external calibration? The certificate should not specify the recalibration date. The decision is that of the laboratory based on need, meaning assurance of test results generated using your equipment. The unbroken chain of calibrations is what provides the Metrological traceability for your results, to meet ISO 17025 clause 6.5.
The calibration interval will vary depending on the type of equipment, in terms of its robustness. The accreditation bodies typically have requirements and or guidelines on this, guided by ILAV (see link below). Some sectors of work and instruments will require a mathematical calculation to determine that the interval is suitable. Typically however, the laboratory itself must look at the need to make the interval shorter due to risk, or justify increasing the interval due to lack of risk. Take an analytical balance for example, that is well looked after. You may typically have it calibrated externally say once a year. Then you perform intermediate checks (verification) before use that verify that the balance is still calibrated and fit for use. Based on risk, you set the range your verified mass should fall within. You should of course, use calibrated mass pieces of a suitable class depending on the type of balance. Then you watch for trends. If you see the performance deteriorating, to minimise risk you would have the next external calibration sooner.
You also asked
What key requirements should I consider when managing all equipment in our lab to insure reliable result? Equipment register?"
Look at Clause 6.4 (Equipment) in ISO 17025, together with clause 6.5 Metrological Traceability where all the requirements are stated. Any that can jeopardise the competency of the laboratory to generate valid results must be considered, risk assessed and controls put in place. For example if am instrument is potentially unstable (drifts) then you would run reference samples (of known result) more often. When those results fail, then the unknown results are not reliable and corrective action must be taken, which may include recalibration.
Also refer to ILAC P10:07/2020 ILAC Policy on Metrological Traceability of Measurement Results and ILAC G24:2007 Guidelines for the determination of calibration intervals of measuring instruments, available from https://ilac.org/publications-and-resources/