The Illawarra region is desperate for 70 platelet donors to come forward on top of those who have already booked appointments over the next three days.

The urgent request comes with the depletion over the holiday period of vital platelet stocks, which is mostly used for the treatment of cancer patients.

With many regular donors on holidays and the number of public holidays over the past two weeks, the supply of platelets has diminished.

"Platelets only last for five days," said Richard Webb, of the Australian Red Cross Blood Service. 

"When we don't collect any platelets at all, it becomes a challenge for us because it impacts on cancer patients who still need treatment regardless of what time of year it is."

About 34 per cent of blood donations go to cancer patients. Platelet donors are able to give a greater quantity of platelets compared with regular blood donations. 

However, it does take a bit longer - about 90 minutes to 110 minutes, compared with the standard one hour for a blood donation.

After 30 years as a blood donor, steelworker Lewis Barrass, of Dapto, made the switch to donating platelets five years ago.

"I've been able to give platelets 12 times this year, so about once a month on my day off, I arrange to come down here," Mr Barrass said. 

"I've had workmates who have had cancer and I've visited them in hospital and seen them receive the platelets of other donors, so I know it makes a difference.

"It's satisfying to think that you're helping someone out. I'm healthy and it doesn't hurt, it's just a bit of my time, that's all."

For first-timer Leah Raynsford, of Wollongong, the switch from regular donor to platelet donor was no big deal.

"They grabbed me for platelets as soon as I walked in the door this morning and I thought 'I'm healthy, why not?"'