To add to this, you should also be getting regular (like twice a year) blood draws done to check where all your nutrient levels are. This way, you can decide which supplements and how much.
Through this, I've learned that my Vit. D supplement works. My multivitamins work, and my B12 supplements work. My previous iron supplement was not working, and I was able to make a change to a different product. Then, six months later, a blood test showed my iron levels back in the normal range.
Honestly, I love comments like this to remind me that HN posters have massive blind spots in knowledge that most people would assume are almost common knowledge for an adult. But beyond that, in the face of seeing 90% of the answer presented in front of you by the prior commenter, where you could basically infer that there must be some be some benefit to taking both, instead of googling it prior to a comment, you reply back with a snide comment assuming the prior poster is a total fool.
Through this, I've learned that my Vit. D supplement works. My multivitamins work, and my B12 supplements work. My previous iron supplement was not working, and I was able to make a change to a different product. Then, six months later, a blood test showed my iron levels back in the normal range.