The fire broke out in the staircase area of the house in Barnacre Close, Fulwood at around 9am.
Three crews from Fulwood, Preston and Penwortham raced to the scene after reports that someone was trapped inside the building.
But when they arrived a woman was already out of the premises receiving treatment from paramedics.
She was taken by ambulance to hospital having suffered burns and smoke inhalation.
Crews wearing breathing apparatus searched the property, but no-one else was inside.
Fire and crime scene investigators were called to examine the property after the blaze was extinguished.
A senior fire brigade spokesman said: “At the moment it is looking like the fire could be suspicious, although investigators are still at the scene trying to establish how it started.
“There is fire damage to the staircase and quite bad smoke damage to the first floor of the property. It looks like it started in the staircase area.
“We sent three crews because that is the normal response when there are persons reported. The 999 call suggested someone might be trapped inside, but our crews searched the house and found no-one else.
“The lady was already out of the building when our crews arrived and was being treated by paramedics. She had burns and had breathed a lot of smoke, but first indications are that her injuries are not serious.”