Supermarket substitution - can I still make caramel with LIGHT condensed milk?

[IHeartKingThistle]

Wanted to make DH Millionaire's shortbread for Valentines Day, but I've been sent light condensed milk - will it still work? It won't be sweet enough, surely?

It's lower fat than normal stuff. Don't know if you can use it instead. How do you normally make your caramel?

I haven't done it for years, I've forgotten!