New Zealand Blood Service’s mobile unit hosted him for the second time in January during its quarterly visit to Invercargill from Christchurch.
Mr Clark first learned about blood donations from his wife, who had been a donor for several years.
When she became pregnant, he decided to keep her pre-booked appointments on her behalf.
"Family members have needed transfusions over the time.
"If people didn’t do that for them, they would probably be dead."
He was undeterred after his first donation, and discovered he was more relaxed the second time.
"I told my workmates, you don’t get any rewards for donating, but you have a sense of contributing to somebody else’s life somehow."
Mr Clark said he got personal satisfaction from the blood donor app telling him his blood was being used.
"I was milking cows and having a s... afternoon, it was hot, boring and then I had a message came through ‘your blood is being used’. I thought, ‘hell yeah!’."
He was trying to imagine what it had been used for: a C-section mum, or leukaemia patients, or someone else who needed it.
New Zealand Blood Service donor relations co-ordinator Lynn Rodeka said a total of 235 units had been donated during the three days the service was based in Invercargill.
"Within the last couple of months, donations had been really positive... people have been booking and donating over this summer holiday period.
"We’ve had a lot of new donors."
People from Invercargill were avid supporters and high repeat donors to the Christchurch-based mobile blood service, with the quarterly donation drive heavily booked well in advance of their arrival, she said.
Southland had a lot of O-positive and O-negative blood donors, which helped the general blood bank.
"We know when we come to Invercargill we get good blood stock for O-negative blood."
O-negative blood was a universal blood type which could be used in any patient.
Blood donations needed to be replenished regularly as it could only be stored for 35 days, Ms Rodeka said.
The mobile service will be visiting: Timaru: Jan 18 and April 9-11; Otago University: Feb 27-29; Oamaru: March 12-14; Gore: March 19-20; Balclutha: March 21; Invercargill from April 16-18.
