Do you need to take magnesium with vitamin d to make it work or work better?

They do not have to: Be combined . We know that calcium and magnesium have some what similar effect when they are in deficiency state . The other piece is when there is shortage of potassium it can not be corrected unless magnesium deficiency is corrected first.

No need: Vitamin d is readily absorbed by the body without the need for additional magnesium supplementation.

Magnesium and Vit D: Vitamin d (d) requires and 'uses up' magnesium (m) to convert from supplements or sun into its active form in the blood. If m levels are low, you may not have enough active d to have calcium absorbed from the intestine. A list of m rich foods can be found at this link: w.Cedars-sinai.Edu/patients/programs-and-services/documents/cp0403magnesiumrichfoods.Pdf d works best with adequate m levels.