His passion for the cause follows a serious accident when he was 16 and the tractor he was driving toppled over a cliff on his parent's farm in France.
He received life-threatening chest injuries and was in a coma for two days.
Twenty units of rare A-negative blood saved his life.
He took up cycling to improve his fitness after he recuperated and since 2004 has cycled 50,000km across 35 countries, as an "international blood ambassador".
He cannot donate blood in France as there is a life-time ban there on donations from people who have received blood.
In New Zealand, blood recipients are unable to donate for at least 12 months although there could also be other factors, too, such as illness, which might prevent donation.
Mr Leblay cannot give blood in New Zealand because there is a donation ban on anyone who has lived six months or more in France, the United Kingdom or Ireland between 1980 and 1996 because of the risk of Creutzfeldt-Jakob (or mad cow) disease.
Mr Leblay and his fiancee, physiotherapist Marion Dumas Cheilletz (25), who donates regularly in France, are spending a few days in Dunedin before continuing north to Auckland, covering about 70km a day, to end their four-month New Zealand visit.
This is the last leg of a journey which has taken them 18 months and involved almost 20,000km by bike in Europe and Asia, as well as Australia and New Zealand.
Their New Zealand visit, which will end late next month, has been supported by the New Zealand Blood Service and Rotary clubs.
On their travels they have encountered a variety of attitudes to cyclists. Switzerland and western European countries were the most tolerant locations - "people may be more used to seeing bicycles on the road there".
And New Zealand?
"A bit scary. Not the best place to bike."
