Proper vitamin D absorption depends on other nutrients. If you are deficient in even one of them, you can have difficulties taking a high enough vitamin D dosage to get your levels up to where they should be.
Most doctors are not familiar with the many health benefits of this critical nutrient. Similarly, they do not know how much we need to receive these benefits.
The RDA for vitamin D is about 400 IU per day for an adult. Just like we've discovered for the health benefits of vitamin C, the RDA is set way too low.
The RDA for vitamin C will prevent scurvy; the RDA for vitamin D will prevent rickets. That's about it. We need considerably more to avoid vitamin D deficiency symptoms that are caused by low vitamin D levels.
For most adults spending the majority of their time indoors, a dosage of 5,000 IU is reasonable. Compare that to the RDA of 400 IU.
What am I getting at here? Say you take a 5,000 IU dose of vitamin D and soon after develop diarrhea, intestinal cramping, or some other digestive problem.
Your doctor will tell you that you are experiencing vitamin D toxicity symptoms. That might make you stop taking vitamin D, which would be a real shame, as the vast majority of us are vitamin D deficient.
So what to do? Learn about what other nutrients vitamin D needs in order to do its job in your body.
First, make sure you are taking a natural vitamin D supplement.
Vitamin D2 is a synthetic drug that drug companies made so they could make more money off of you. Our bodies have a much harder time properly utilizing it.
Vitamin D3 still not helping?
You could be low in magnesium - see magnesium and vitamin D for an explanation of this relationship.
I recommend magnesium oil (magnesium chloride) for maximum magnesium absorption. Most oral supplements are difficult for the body to utilize and can cause diarrhea if you take too much at one time. It makes it difficult to get enough into your body to raise your magnesium levels.
Magnesium oil is just sprayed onto your skin and rubbed in. That means no worries about any digestive troubles or overdose. You'll skin will absorb only as much as it needs.
What if you are still having problems?
It could be a zinc deficiency.
Magnesium is the probably the most important cofactor of vitamin D, but zinc plays a role too. And most of us are deficient in zinc too. See list of minerals for immune health for an explanation on how to take zinc.
That should clear up most people's problems with vitamin D absorption. If not, there are a few other things to consider.
Perhaps you are missing one or more of the rest of the vitamin D cofactors.
Besides magnesium and zinc, there is vitamin K, boron, and vitamin A. But we only need tiny amounts of these nutrients for good vitamin D absorption, so taking an organic whole food supplement should take care of that.
You also might want to switch over to a dry vitamin D if you are using a vitamin D that comes in oil.