About 6,000 community pharmacies in England are being advised to start working to rule in two weeks, unless an agreement can be reached with the government on a new NHS contract.
The National Pharmacy Association (NPA) is urging its members to take action because they have yet to receive any confirmation of an increase in funding for this or next financial year.
Action could involve reducing their opening hours and cutting other services, such as delivering medicines to people's homes.
The government said the move would cause "unnecessary disruption for patients" and a settlement with pharmacies was already being worked on.