(Reuters) -UnitedHealth Group has brought back online the pharmacy systems at its Change Healthcare technology unit following the Feb. 21 ransomware hack that disrupted the U.S. healthcare system.

The healthcare conglomerate expects the payment platform to be functional and begin restoring the medical claims network starting mid-March. UnitedHealth is likely to need several months to make a full recovery, according to security experts.

The following are some of its largest businesses and UnitedHealth's plans for how and when to fix them:

PRESCRIPTION DRUG PROCESSING

Change Healthcare acts as a financial clearing house connecting the companies that managed drug benefits called pharmacy benefit managers with pharmacies. Without that technology, pharmacies cannot verify if a patient is covered by a healthcare plan for a particular drug and how much that patient was expected to pay out of pocket.

As of March 13, all major pharmacy and payment systems are up and more than 99% of pre-incident claim volume is flowing, UnitedHealth said.

There are still pharmacies that remained offline and there is disruption for infusion pharmacies and interruptions for some Medicaid fee-for-service customers, the company has said.   

PRESCRIPTION DRUG COUPONS

UnitedHealth's tech unit processes discounts that manufacturers offer on some of their drugs through electronic coupons. Pharmacies could not apply many of these coupons when Change's systems went down, leaving patients to pay full price for the drugs upfront. Some manufacturers, including Eli Lilly, offered to reimburse patients for the amount their coupons would have covered.

UnitedHealth says its pharmacy network reconnection allows the majority of coupons it manages to again be processed. Coupons handled by rival McKesson's RelayHealth have not been disrupted.

INSURANCE CLAIMS

Healthcare providers including hospitals submit health insurance claims to Change, which sends them to health insurance companies to evaluate and process. After the cyberattack, these providers lost a primary means of processing payments for their services through patients' healthcare plans.

Beginning the week of March 18, UnitedHealth will begin bringing up the claims system for reconnection and testing in a phased manner. It recommends that customers use a workaround by reconnecting through an alternate network in the interim.

It said full service will be restored once testing has been completed.

The company said some providers may need more restoration work before they can submit claims and that there are some who have not been able to implement workaround solutions.

(Reporting by Patrick Wingrove in New York and Sriparna Roy in Bengaluru; Editing by Bill Berkrot and Sriraj Kalluvila)