How many vitamins should I take?

In humans there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9 water-soluble (8 B vitamins and vitamin C).

The following table gives a summary of these vitamins, recommended daily allowance, deficiency and overdose information:

Vitamin name	Chemical name	Solubility	Recommended dietary allowances (male, age 19–70)	Deficiency disease	Upper Intake Level (UL/day)	Overdose disease
Vitamin A	Retinoids (retinol,retinoids and carotenoids)	Fat	900 µg	Night-blindness and Keratomalacia	3,000 µg	Hypervitaminosis A
Vitamin B₁	Thiamine	Water	1.2 mg	Beriberi	N/D	?
Vitamin B₂	Riboflavin	Water	1.3 mg	Ariboflavinosis	N/D	?
Vitamin B₃	Niacin	Water	16.0 mg	Pellagra	35.0 mg	"Niacin flush"
Vitamin B₅	Pantothenic acid	Water	5.0 mg	Paresthesia	N/D	?
Vitamin B₆	Pyridoxine	Water	1.3-1.7 mg	Anemia	100 mg	Impairment of proprioception
Vitamin B₇	Biotin	Water	30.0 µg	None identified	N/D	?
Vitamin B₉	Folic acid	Water	400 µg	Deficiency during pregnancy is associated with birth defects, such as neural tube defects	1,000 µg	?
Vitamin B₁₂	Cyanocobalamin	Water	2.4 µg	Megaloblastic anaemia	N/D	?
Vitamin C	Ascorbic acid	Water	90.0 mg	Scurvy	2,000 mg	Refer to Vitamin C megadosage
Vitamin D	Ergocalciferol and Cholecalciferol	Fat	5.0 µg-10 µg	Rickets and Osteomalacia>	50 µg	Hypervitaminosis D
Vitamin E	Tocopherol and Tocotrienol	Fat	15.0 mg	Deficiency is very rare; mild hemolytic anemia in newborn infants.	1,000 mg	?
Vitamin K	Naphthoquinone	Fat	120 µg	Bleeding diathesis	N/D	?