"Even Treasury officials have been saying prevention gets you four times better return for every health dollar you invest than if you invested in services at the other end of the health spectrum," Mr Hague said.
The Greens would also look at correcting shortcomings in the health workforce.
"We have crises in nearly every area of the health workforce. There's dwindling New Zealand-trained doctors, nurses, pretty much every occupation your can think of.
"We've been recruiting overseas for staff which works in the short-term but longer-term stymies the hopes of those looking for work when they graduate.
"For those graduates their only hope is to head overseas," he said.
His party wants to get the health officials, trainees and professionals together and ask them to find solutions, aware of the financial constraints a government would have to work with.
"What they figure out is what we would do ... they all say it's worth a go because so far nothing else has worked."
Mr Hague said the other major issue was inequalities.
"The life expectancy between non-Maori and Maori has not been getting any closer. We say the priority must be on improving the health of those with the poorest health status ahead of further improving the health who are already the healthiest.
"That's quite a shift for our health system because typically a lot of funding goes into new medicines or new imaging technology. But those are things that tend to favour those with better health already."
The Greens' themes on health were interconnected, focused on preventing illness and improving primary care as a priority.
Mr Hague also chimed in to the issue of transport assistance for people travelling to Palmerston North for services. He said in its current form the distance threshold of a minimum of 80km meant many Wanganui people would miss out on any help.
"And we're going to see more regionalisation of health services across the country. This will mean a hollowing-out of services, which means those in rural New Zealand, especially, will find services harder to get."
Support must be available to help people access those services, he said.