From January 2018 Irn Bru will contain approximately 50% less sugar.
The move is part of a sugar-reduction programme by AG Barr before the Soft Drinks Industry Levy comes into effect in 2018.
Regular Irn Bru sugar content will reduce from 10.3g to 4.7g per 100 millilitres. This will reduce the calorie count per can from just under 140 to about 66.
Regular Irn Bru will still remain a sugary drink but will now be blended with a mix of low calorie sweeteners including aspartame, a source of phenylalanine.
A spokesperson from A.G. Barr said: "From January 2018 Irn Bru will continue to be made using the same secret Irn Bru flavour essence, but with less sugar.
"The vast majority of our drinkers want less sugar in their Irn Bru so that's what we're now offering.
"We know that our loyal drinkers love Irn Bru for its unique great taste and we've worked hard to deliver this.
"We ran lots of taste tests that showed most people can't tell the difference – 9 out of 10 regular Irn Bru drinkers told us we had a good or excellent taste match.
"Most shoppers can expect to buy Irn Bru with reduced sugar from later this month. Give it a try when it comes out."
The Soft Drinks Industry Levy is a key part of the government’s childhood obesity strategy, and was first announced at Budget 2016. The tax will see firms to pay extra tax on drinks containing more than 5g of sugar per 100 millilitres.
The new tax would see the North Lanarkshire drinks firm paying an extra 24p tax for every litre of original recipe juice they produce.
It was originally estimated that tax would, in its first year, raise £520m a year. Though a year later the estimate dropped to £400m after soft drinks companies started to cut sugar.