Most GP practices in England have suffered disruption as a result of the major global IT outage, according to the NHS.
But it said there is currently no known impact on 999 or emergency services.
GP surgeries have said they are unable to access patient records or book appointments due to the outage.
Global IT outage: Follow live
Pharmacies also reported issues with accessing prescriptions from GP surgeries and said this would affect the delivery of medicines to patients.
NHS England has been contacted for comment after GP practices across England took to social media to report they cannot access the EMIS Web system.
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