My primary care clinician told me to lift as heavy as I could - but to build up to slowly. There is lots advice on the internet and Instagram on how to do this. You need to challenge your bones but not hurt yourself. I think the rule of thumb is if you can get to 12 reps at weight you should go up in weight. There is something called the 85% level - this is from the AI in Google search "Lifting at the 85% level refers to using 85% of your one-rep max (1RM) to challenge your skeleton. This high-intensity mechanical stress forces your bones to adapt and remodel. It is one of the most effective and research-backed methods to increase bone mineral density (BMD) and prevent age-related bone loss." So you want to lift heavy but safely and build up to it.