The air ambulance is not funded by the government
Rising fuel prices could cost an air ambulance service an extra £130,000 a year, its staff estimate.
The County Air Ambulance, which operates across much of the West Midlands, is a charity which needs £5.6m to operate three helicopters.
Spokesman Steve Parry said when a fixed price fuel deal finishes in October, its hourly fuel costs will rise from £104 to £170.
The charity is not funded by the government or National Lottery.
The air ambulance's fuel supplier gives the fuel at a reduced rate.
The supplier has warned staff that the prices will go up from October.
Mr Parry said: "We anticipated an increase in our operational budget at the beginning or the year and adjusted our fundraising target accordingly.
"However, there is no doubt that rising fuel costs of this magnitude will place additional financial pressure on the charity at a time when we are committed to making improvements to our service."
The air ambulance serves Herefordshire, Worcestershire, Staffordshire, Shropshire and the West Midlands.