Vitamin D3 - because I'm chronically low without. Calcium - I only take when I cut back on dairy. Too much calcium risks kidney stones, did you know that? Vitamin C - small skin injuries on lower legs seem to heal better; I only take when I am not eating citrus. Too Much Vitamin C Not Good for Diabetics' Hearts Multi-vitamin - just cuz doc says to. Fish oil - I just take this in winter. I stopped getting the terribly dry skin. Worked for the dog, then worked for me!
I personally look at supplements as drugs and only take what I really feel I need to.
I have gone back and forth on supplements for years now, never quite making up my mind what I should or shouldn't do.
A few months back, I started taking Magnesium Malate, NAC, and VitaminD3 because I was feeling exhausted all of the time. I feel 100 times better now, but like a fool I started them all at the same time, so I have no clue which one (if any) is responsible for the improvement.
I take some supplements because I tested low (D3, but then I added K2 because it works with D3), some because the soil does not provide as much to food as it used to (magnesium, potassium, multivitamin), some for other health conditions (garlic, krill oil, vitamin c, COQ10, turmeric), some for just in case they do work ( don't think I have any in this category at the moment)
Vitamin K2 mk7 is the only one. My labs say I'm not deficient in any area. I prefer to get everything I need from what I eat. My wife is always low on vitamin D even though she supplements high doses daily and takes a multi vitamin with it in too. Reading a lot, I have little faith in supplementation. No guarantee that what you think you are getting will find it's way to where it needs to go to help a deficiency.
I take D3 B complex, a multivitamin, magnesium and a supplement called Agilease. I also use essential oils which have enabled me to get off my daily dose of ibuprophen, (had been on 800mg 4x per day for years) in addition to the diabetes, I have fibromyalgia and Hashimotos disease