What to do when an employee calls in sick
Let’s start with a positive. The fact that they telephoned in is a good thing!
Unless they are genuinely prevented from doing so, it is really important that your employees telephone in person, by a specified time, and to a designated person (ideally their immediate manager). A text, or an email, or a message via a third party is not good practice.
If the designated person is unavailable, then it is acceptable to call and speak to the employee later in the day (health permitting).
While a little discretion and common sense may be needed depending on the nature of their ill health, it is quite acceptable for you to ask what is broadly wrong with them, and how long they expect to be off sick for. If they are up to it (again with some discretion) double check if there are any pressing work issues you need to be made aware of or meetings that may need to be rearranged. The vast majority of employees will not want things to go wrong when they are off and will be happy to provide a bit of information to keep things ticking over in their absence.
You should not, however, ask intrusive questions about their health or put them under undue pressure when asking for an update on work issues that might need to be handled in their absence.
If their ill health is something that could be passed on to colleagues (such as influenza) then you might want to discuss options for them working remotely (when they are feeling a little better) to avoid spreading it throughout the team/business.
If the absence is continuing for longer than a day or two, make arrangements to speak to the employee again to get an update on their health and check in again about work issues that may need covering.