Blood demand is at a 12-year high and plasma is even more in need, sparking a call for Australians to roll up their sleeves.

The Red Cross is urging 100,000 Australians - the same number who will fill the MCG for the AFL grand final on Saturday - to donate for the first time over the next year.

More than 560,000 people actively donate to maintain the population's blood and plasma supply.

However new donors are needed to keep up with the growing nation.

"We know 100,000 people will show up if they have a compelling reason to do so, like cheering on their team at the MCG," executive director of donor experience Cath Stone said.

"We're calling on 100,000 people to find their reason to show up to donate blood and plasma."

Ms Stone said the reason could be for a family member battling cancer or simply the free party pies or milkshake after you donate.

AFL premiership player Ben Brown and his wife Hester have joined the campaign to encourage more people to donate, with the cause close to their hearts.

Brown's cousin Grace is a cancer patient who relies on blood and plasma to survive.

"Grace has survived leukaemia twice but her body is no longer capable of fighting infections or illnesses on its own," he said.

"Grace requires blood products weekly for the rest of her life, so we want to encourage others to be brave like her and roll up their sleeves to donate at Lifeblood."

Demand for blood has increased 10 per cent in the past four years while the demand for plasma is even more, reaching an all-time high.

The Red Cross now collects more blood than plasma with the substance used to treat more than 50 serious medical conditions.

Ms Stone said with Australia's ageing population and advances in treatment options, more donors are needed.

"We estimate just three per cent of the eligible population in Australia currently donates and that tells us there are a lot of reasons why people don't donate," she said.

"We're asking people to find just one reason why they should."