First, check out NHS Inform self-help guide which provides information about when to use self-care, and when to seek medical help: NHS Inform self-help guide
If someone does not want to go to hospital, it is still important that they access the support of their GP and NHS community team – there are care and medications that can be provided in the home that can help to keep someone as comfortable as possible.  
It is important to recognise that some people who are very unwell with COVID-19 will have valid reasons for not wanting to go to hospital.  Indeed, for most people, home will be the most comfortable environment in which to be unwell. 
However, for some people, hospital will be able to provide interventions that can support them to recover.
It is important that the individual makes the decision that is right for them, and this should be done in discussion with their GP or the healthcare professional that knows them best.   This kind of discussion can be recorded in an Anticipatory Care Plan. You can learn more about Anticipatory Care Planning here: Anticipatory Care Planning
Further information about what a friend or family member can do to support someone at home who is seriously ill at home with COVID-19 is available here: Helping someone you care about
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