Hundreds of workers are taking part in their second 24-hour strike from 2200 BST on Tuesday over the transfer of NHS Logistics to German delivery firm DHL.
Unison is expected to propose a motion at the Manchester conference calling for a review of NHS privatisation.
The government said disruption from last week's walkout was minimal.
A Department of Health spokesman said there had been no reports of any major problems, and hospitals and GPs had contingency plans in place - many can also order their own supplies, rather than go through NHS Logistics.
And he added the transfer, which takes place at the beginning of October, would "help save
Latest Articles
Hundreds of workers are taking part in their second 24-hour strike from 2200 BST on Tuesday over the transfer of NHS Logistics to German delivery firm DH...
