Vitamin d is so easy to be too low in, even if you walk around in the sun in shorts or a sundress. 2000 is for kids is about right. They can skip it if they were in bathing suit in the sun for hours. For older people most need at least 5000 IU a day.
Magnesium (not oxide, that’s worthless laxative) is another very important supplement to take daily. Vitamin k as well.
Your vitamins should be sourced carefully, not from China, not cheap.
You should expect to actually feel or see or measure results from anything worthwhile. A good vitamin d level plus sleep, and no huge stressors, you should get through the winter with no colds or flus. Taking magnesium citrate or asporotate before bed means you should sleep deeply and suffer no constipation ever. Vitamin k should prevent bone breaks or teeth problems.
When feeling ill, vitamin c and zinc should help you get well very quickly.
Vitamins should be chewable or in a capsule. Tablets are difficult to digest.
I sometimes take Calm (magnesium citrate powder) at night. This winter I switched to magnesium gel on my feet as I’ve heard it’s better absorbed through the skin rather then moving quickly through the digestive tract. It smells like stinky cheese so it’s not for the summer.
I’ll have to check out vitamin K-I never thought about that before.
I have a hard time believing all these chemically extracted vitamins are as good as when they come from actual food. Need vitamin D? Drink milk and get some sun. Need B12? Eat green veggies. Need vitamin C? Eat fruit. Need all of the above and more? Eat Kale.