It's understood a rescue helicopter was dispatched.
A policeman on the scene said it was "lucky there were no cars coming in the other direction at the time".
Although the truck was off the road, there was a large amount of debris blocking the road and milk gushing from the tanker and into the drain at the side of the road.
At the time, police asked motorists to avoid the area as lengthy delays were expected.
A crane was brought in just before 5.30pm to remove the toppled tanker and the road finally reopened around 7pm.
A Hawke's Bay District Health Board spokesperson said a man in his 50s was in Hawke's Bay Hospital in a stable condition.
The last Fonterra truck crash in Central Hawke's Bay occurred in 2007, when a tanker crashed into three houses in Waipawa after the driver reportedly choked on a lolly and lost control of the truck.
The driver received a broken nose and cuts to his face. Two of the three houses were demolished.
