But Dr Ronald Lam Man-kin, a Department of Health assistant director who is in charge of traditional Chinese medicine, said those who bought non-registered medicine 'in a reasonable quantity', unaware of the products' registration status, and for self-use, could be exempted.

So could Chinese herbalists who prepared the medicine for their patients within their clinics.

'The spirit behind the law is to stop people from selling a large quantity of non-registered drugs, which can endanger people's health,' Lam said.

By October, 11,280 products were covered by temporary licences that would qualify them to be sold after Friday - meaning that they have satisfied the department's safety requirements.

But applications for 5,400 products - about a third of some 16,700 products - on sale were rejected, and they have to be taken off the shelves.

Lam said of the temporarily licensed products, only nine had so far qualified for a full licence, which certifies that a product satisfies requirements in safety, quality and efficacy.

All products will eventually need a full licence.

Although some products already carry labels with a licence number, this will not be mandatory until December 1 next year.

'Market pressure will force sellers to include the labels before the deadline,' Lam said.

But Patients' Rights Association spokesman Tim Pang Hung-cheong said a one-year gap between compulsory registration and labelling was too long.

'Even if they needed time to modify the labels, a few months would be adequate,' he said.

'Many users of traditional Chinese medicine are old people. One cannot expect them to know how to get online. It would be best if they could directly tell from the package,' he said.

Hong Kong General Chamber of Pharmacy chairman Lau Oi-kwok said about 10 per cent of their products would have to be withdrawn from sale on Friday.

'We will not suffer too much loss, as we can always return them to the suppliers,' he said.

Lam said monitoring and inspections would be stepped up after Friday with a team of 100 officials, including 27 pharmacists.

He urged people who had unregistered products at home to dispose of them as soon as possible, as he said 'the products' safety cannot be guaranteed'.

A product is deemed safe after it passes tests to meet requirements on heavy metals and toxicity, pesticide residue and microbial limits.

Quality requirements refer to a medicine's ingredients, shelf life and manufacturing method, while efficacy refers to the drug's effectiveness for treating certain conditions. Some products may require clinical trials to prove efficacy.

Lam said there was no timetable yet for upgrading temporary licences into full licences, but it would be done step by step, considering the long history of Chinese medicine in Hong Kong.