I've heard a lot of excuses over the years, ranging from the usual, "I'm busy," or "I don't like needles," to "I don't think they'd want my blood," or even, once: "I don't like the idea of my blood in someone else's body."
After the first time I donated blood I adopted a few of these excuses myself, partly because whenever the blood centre rang me to see if I could donate again it made me feel as though I had a clingy boyfriend with Twilight-esque tendencies and in true teenager fashion I just didn't want to be tied down.
I did eventually figure out the root of my reluctance. It was that I didn't particularly like the pain involved, however small. Once I came to the conclusion the free chocolate biscuits they provide afterwards made it all worthwhile, I gritted my teeth and finally said yes to my vampiric significant other.
It's about five years on, now, and I donate every time they call me - partly for the biscuits - but mostly because I know I'm helping other people who desperately need it, be it the people who regularly require transfusions due to a medical condition, or the people who wrap their cars around trees.
The New Zealand Blood Service comes to Wanganui for a couple of days each month, getting roughly 100 to 120 people through their doors each time.
When I went to donate on Wednesday, it was particularly quiet, Delwyn Brigham, a registered nurse, told me.
There were a few other people dotted around the room, but the low volume of blood-givers meant I had the snack table all to myself afterwards.
There's really nothing to donating. You fill out a form, and get your iron levels tested with a simple prick to the side of your thumb. For women, iron levels must be from 120-175, while men need 130-185 to be eligible.
The next step is climbing into a chair and sticking your arm out while the nurse disinfects it and finds the vein. Once the needle's in, it's generally smooth sailing from there.
It takes around the six-minute mark to take about 470ml of blood, although the fastest Mrs Brigham had seen was three minutes.
Adverse effects were only occasional with fainters being few and far between.
"Some people notice no difference," said Mrs Brigham.
For myself, after donating I would be sleepy, and would get a little more puffed walking up stairs than usual. Apart from that, there was never any issue.
Sabine Hormann was donating for her 25th time on Wednesday, and said she'd never felt any different afterwards.
"My dad actually did it when I was a child in Germany," she said.
"I thought it was pretty cool.
"It's a very easy thing to do for someone else. If you're healthy, do it."
Mrs Brigham said only 4 per cent of those eligible in New Zealand actually donated, a number which was consistent throughout the country.
"We understand people are busy in their lives, but it's still a situation that can make a huge difference to whoever is getting that blood," she said.
"They are reliant on the donating public."
Mrs Brigham said Wanganui donors were particularly reliable, but the blood service was in need of more new donors, as many full blood donors had started donating plasma instead, which allowed them to give more often and greater amounts.
She thought there was no main reason people didn't donate, but guessed it could be because they were too busy and hadn't thought about it.
They had some people afraid of needles who donated anyway, she said.
"Boy, do I admire those people."
Mrs Brigham wanted to thank the donors they already had, and said other Wanganui residents should "come in and give it a go".
"For many people it's just such a small thing to do to help someone else.
"If that someone else was someone you knew, you would be so grateful."
The NZ Blood Service will be coming to Wanganui again on April 22 at the War Memorial Hall, so call 0800 448 325 (0800 GIVE BLOOD) to make an appointment.