The change takes place with immediate effect - but community hospitals and mental health centres will remain at two visitors.
NHS Forth Valley said it took the action because of rising cases at the hospital and an in the community.
But it said it would closely monitor the situation, and lift restrictions as soon as possible.
An essential visit is one where it is imperative that a relative or friend is allowed to see their loved one in a number of exceptional circumstances.
These include end of life care, for patients with a mental health issue such as dementia, autism or learning disabilities where the absence of a visitor would cause distress, to support a child or baby in hospital, or any other situation where clinical staff assess that it is essential to involve family or carers for ethical or patient safety reasons.
For ante-natal appointments and maternity scans, one person can accompany people to to all appointments.
Birthing partners can be present throughout.
There are also exceptions for neo-natal visiting, while on the children’s ward, patients can have visits from both parents or carers who should observe social distancing.
All visitors are asked take a lateral flow test before attending, maintain physical; distancing in wards and communal areas, and wear a surgical face mask which is available at the entrance.
They should also wear PPE if required or asked to do so by a member of staff.
The hospital’s restaurant remains closed to the public.