Is this nutritional supplement powder genuine, and is it safe for an elderly person to take?

It's thoughtful of you to think this through before giving it to an older family member. Supplement powders like this can generally be safe for elderly individuals, but age often brings other health conditions or medications that need factoring in, like kidney function or drug interactions. As for authenticity, buying only through a trusted pharmacy or the official product page is the safest way to be sure of what you're getting. Do run it by their doctor first, especially if they have any chronic conditions.