Although the journey had been meticulously planned, his arrival in Masterton was a day ahead of schedule, he said.
"Mostly I just wanted to get home to my wife so it gave me extra momentum I wouldn't have had otherwise."
He began the trip on December 29.
"I've loved every minute of it - and in parts it's been very emotional. You can start off doing something and do all the plans but it's not until the start that you realise that it's a pretty big undertaking.
"I was certainly shedding some tears coming into Masterton."
Cycling 80km to 150km a day, Mr Caldwell hopes to make it to Bluff by the end of the month.
A support van has been provided by Eastwood Motor Group, which is also paying for petrol costs incurred during the ride.
Mr Caldwell's Roubaix Elite carbon-fibre road bike was donated for the task by Penny and Todd Hart of Carterton.
Being diagnosed with type 2 diabetes about 10 years ago was a "real wake-up call", Mr Caldwell said.
Since then he had shed about 20kg and was now much fitter.
During his journey he had met many people who had been touched by the condition, he said.
"Everywhere I've travelled people have seen the van and and the flyers and they've just come up and handed over money.
"In most cases those people have relatives who had the condition, and for whatever reason they've passed away ... it's quite overwhelming."
Mr Caldwell leaves for Wellington via the Rimutaka Rail Trail on Friday.
To make a donation towards Mr Caldwell's Cape Reinga to Bluff trip, go to the website www.diabeteswairarapa.org.nz
