Do I need vitamin K with calcium?
Many combined formulas include it, and vitamin K2 contributes to the maintenance of normal bones. If you are on anticoagulants, check with your GP first - vitamin K interacts with them directly.
Which calcium is best absorbed?
Citrate is generally taken up more readily than carbonate and sits better with digestion. Carbonate packs more calcium per tablet, so it is a trade-off. The form is on the pack.
Can I get enough from diet?
Many people can - dairy, tinned fish with the bones in, tofu, and leafy greens all contribute. Vitamin D is the harder one in a British winter, whatever your diet.
Should I take calcium and iron together?
Better apart. Calcium interferes with iron absorption, so if you take both, space them by a few hours.