Which are recommended After hours / 24 hours pharmacies in SG?

Agree with Diana, the pharmacy at Mustafa Centre is one of them and it is awesome! My old job required me to be on standby and I had the super irregular hours. Whenever I needed to buy groceries, I'd stop by Mustafa Centre and the pharmacy will also be my go-to place to stock up on aspirin and other first aid stuff. Their selection, in my opinion, is much better than any other pharmacy. Guardian has 24 hour pharmacies but they are located in the Departure transit areas. The Guardian at The Shoppes at Marina Bay Sands is opened till midnight on Fridays and Saturdays and Guardian Tampines North Drive (opposite IKEA) on Saturdays and Sundays.