13 Vitamins Your Body Needs

You need A, C, D, E, K, and 8 different B vitamins every day. You can get all of these vitamins from the food you eat. Also, with the help of sunlight, your skin can make vitamin D. Your own body can also make vitamin K.

There are fat-soluble vitamins and water-soluble vitamins.

Fat-soluble vitamins, which means they stay in your body until you need them:

Vitamin A
Vitamin D
Vitamin E
Vitamin K

Water-soluble vitamins, which means they are used by your body right away:

Thiamin (Vitamin B1)
Riboflavin (Vitamin B2)
Niacin (Vitamin B3)
Vitamin B6
Vitamin B12
Vitamin C
Biotin
Folic Acid (also called Folate)
Pantothenic Acid

You can get the vitamins and minerals that you need each day by eating fresh fruits, vegetables, grains, dairy products, and meats.
Vitamin pills cannot replace eating healthy foods.

Note:
A doctor may recommend taking vitamin supplements for people with certain health problems, for vegetarian or vegan diets, or for pregnant or breastfeeding women.

How do you know when your body needs these vitamins and when do you know when to take the vitamins again in case your body hasn't used the ones that are still in your body??

I would say by the way your body talks back to you. If you weren't getting all the vitamins and minerals you needed through the food you eat everyday, things would start going wrong with you, and your body would definitely let you know. One example... a vitamin D deficiency can cause rickets in children, and cause osteomalacia in adults.

You know when to take the vitamins again just by eating a "healthy balanced diet everyday". The post above was talking about eating food, not taking vitamin supplements. From all the articles I have read, your body will use the vitamins when your body needs them, and you will replace them by eating a healthy balanced diet everyday. Balanced is the key.

Note:
Vitamin supplements may be useful when they fill a specific identified nutrient gap that cannot or is not otherwise being met by a persons intake of food.

And I'm not talking about people who have serious illnesses or diseases, they need to get all their advice and help from their doctor.