Do I need a manganese supplement?
Most people get enough from food – wholegrains, nuts and tea are ordinary sources. It is not one to take speculatively.
What is the difference between chelated and citrate?
Both are forms intended to be well absorbed and the practical difference is small.
Is it in my joint supplement already?
Very possibly – manganese appears in many bone and joint formulations. Check before adding it separately.
How much should I take?
Follow the pack. This is a trace mineral needed in milligrams, not a nutrient where more achieves more.