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Vitamins Guide

Select any of the 13 fat-soluble and water-soluble vitamins to see its function, deficiency symptoms, food sources, and Daily Value in detail.

Fat-soluble vitamins

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Vitamin A (Retinol)

A fat-soluble vitamin involved in vision, skin and mucous membrane health, and immune function.

Key functions

  • Involved in synthesizing rhodopsin, the visual pigment that maintains eyesight in low light.
  • Keeps skin and mucous membranes (eyes, respiratory tract, digestive tract) healthy, helping defend against pathogens.
  • Supports normal immune cell function, growth, and development.

Possible deficiency symptoms

  • Night blindness (reduced vision in low light)
  • Dry eyes, corneal damage
  • Skin flaking, lowered resistance to infection

Key food sources

Carrots, spinach, pumpkin and other orange/dark-green vegetables (beta-carotene)Animal liverEgg yolkMilk and dairy products

Daily Value (DV): 900 mcg RAE

Overdose cautions

Being fat-soluble, it can accumulate in the body, and long-term excess intake may cause headaches and liver damage. Excess intake during pregnancy has been linked to birth defect risk, so pregnant women should be cautious about supplements.

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Vitamin D (Calciferol)

Helps the body absorb calcium and phosphorus for bone health, and is the one vitamin the skin can synthesize from sunlight.

Key functions

  • Promotes calcium and phosphorus absorption in the intestines, keeping bones and teeth strong.
  • Also thought to play a role in muscle function and immune regulation.
  • The only vitamin the body synthesizes on its own when skin is exposed to sunlight (UVB).

Possible deficiency symptoms

  • Children: rickets (soft, bowed bones)
  • Adults: osteomalacia, increased osteoporosis risk
  • Muscle weakness

Key food sources

Fatty fish such as salmon and mackerelMushrooms (especially sun-dried)Egg yolkSunlight exposure itself (roughly 15-30 minutes a day)

Daily Value (DV): 20 mcg

Overdose cautions

Long-term excess from supplements can cause hypercalcemia (excess blood calcium) and kidney stones. Excess from sun exposure alone has not been reported.

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Vitamin E (Tocopherol)

A powerful antioxidant that protects cell membranes from oxidative damage.

Key functions

  • Acts as an antioxidant, protecting the lipids in cell membranes from damage by free radicals.
  • Also supports blood vessel health and immune function.
  • Works alongside other antioxidant nutrients such as vitamin C and selenium for a stronger combined effect.

Possible deficiency symptoms

  • Very rare with a normal diet
  • Severe deficiency can cause hemolytic anemia and neurological problems (mostly in people with fat-malabsorption conditions)

Key food sources

Almonds, sunflower seeds and other nuts/seedsVegetable oils (sunflower oil, olive oil, etc.)Spinach, avocado

Daily Value (DV): 15 mg

Overdose cautions

Very high long-term supplement doses can impair blood clotting and raise bleeding risk, so anyone on blood thinners (like warfarin) should consult a doctor before taking high doses.

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Vitamin K (Phylloquinone/Menaquinone)

Helps blood clot normally and also plays a role in bone metabolism.

Key functions

  • Essential for synthesizing several clotting-factor proteins needed for normal blood clotting.
  • Also activates a bone protein (osteocalcin), linking it to bone health.
  • Partly synthesized by gut bacteria as well.

Possible deficiency symptoms

  • Tendency for bleeding not to stop easily (newborns, who have low vitamin K reserves, need particular attention)
  • Dietary deficiency is rare in healthy adults

Key food sources

Kale, spinach, broccoli and other leafy greensNatto (fermented soybeans)Soybean oil, canola oil

Daily Value (DV): 120 mcg

Overdose cautions

No excess effects have been reported from food alone, but anyone on blood thinners like warfarin should keep their vitamin-K-rich vegetable intake fairly consistent, since sudden large changes can affect the medication's effect.

Water-soluble vitamins

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Vitamin B1 (Thiamine)

Needed for converting carbohydrates into energy and for normal nerve function.

Key functions

  • Acts as a coenzyme in the metabolic process that converts carbohydrates (glucose) into energy.
  • Involved in maintaining normal nerve cell function.
  • Being water-soluble, it isn't stored in large amounts, so steady daily intake is needed.

Possible deficiency symptoms

  • Beriberi (leg numbness/swelling, heart failure in severe cases)
  • Fatigue, loss of appetite
  • In severe cases, neurological problems (Wernicke-Korsakoff syndrome, usually linked to alcohol dependence)

Key food sources

PorkBrown rice, whole grainsLegumes, nuts

Daily Value (DV): 1.2 mg

Overdose cautions

No well-established overdose risk from food or typical supplement use has been reported for this vitamin.

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Vitamin B2 (Riboflavin)

A water-soluble vitamin involved in energy metabolism and skin/mucous membrane health.

Key functions

  • Acts as a coenzyme in several metabolic processes that convert carbohydrates, fats, and protein into energy.
  • Helps keep skin, eyes, and mucous membrane tissue healthy.
  • Sensitive to light, which is why milk and similar products are often stored in light-blocking containers to reduce nutrient loss.

Possible deficiency symptoms

  • Cracking at the corners of the mouth (angular cheilitis)
  • Glossitis (inflamed tongue)
  • Dermatitis, eye discomfort such as sensitivity to light or redness

Key food sources

Milk and dairy productsEggsMushroomsAlmonds and other nuts

Daily Value (DV): 1.3 mg

Overdose cautions

No well-established overdose risk from food or typical supplement use has been reported for this vitamin.

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Niacin (Vitamin B3)

A key energy-metabolism vitamin involved in hundreds of metabolic reactions in the body.

Key functions

  • Needed for numerous energy-producing enzyme reactions in carbohydrate, fat, and protein metabolism.
  • Also involved in nervous system and digestive function and skin health.
  • Partly synthesized in the body from the essential amino acid tryptophan.

Possible deficiency symptoms

  • Pellagra (a deficiency disease combining dermatitis, diarrhea, and cognitive decline)
  • Loss of appetite, fatigue

Key food sources

Chicken, tuna and other meat/fishPeanuts and other nutsBrown rice, mushrooms

Daily Value (DV): 16 mg NE

Overdose cautions

High-dose supplements (in the nicotinic acid form) commonly cause a "niacin flush" β€” reddening and burning in the face and upper body β€” and severe cases can affect liver function.

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Vitamin B5 (Pantothenic acid)

Involved in carbohydrate/fat metabolism and hormone synthesis, and found widely in almost every food.

Key functions

  • A core component of coenzyme A, essential for energy metabolism.
  • Involved in synthesizing fatty acids, cholesterol, and some hormones and neurotransmitters.

Possible deficiency symptoms

  • Deficiency is very rare since it's found in almost all foods
  • Fatigue and tingling in the hands/feet have been reported in cases of severe overall malnutrition

Key food sources

EggsMushroomsAvocadoMeat, whole grains

Daily Value (DV): 5 mg

Overdose cautions

No well-established overdose risk from food or typical supplement use has been reported for this vitamin.

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Vitamin B6 (Pyridoxine)

A vitamin involved in protein metabolism and neurotransmitter synthesis.

Key functions

  • Acts as a coenzyme needed for amino acid (protein building-block) metabolism.
  • Involved in synthesizing neurotransmitters such as serotonin and dopamine.
  • Also needed for synthesizing hemoglobin in red blood cells.

Possible deficiency symptoms

  • Anemia
  • Dermatitis, cracking at the corners of the mouth
  • Peripheral nerve problems (tingling in hands/feet)

Key food sources

Chicken breast and other lean meatsBananasPotatoesBrown rice, whole grains

Daily Value (DV): 1.7 mg

Overdose cautions

Very high long-term supplement doses have been reported to cause peripheral neuropathy (tingling, numbness), so while ordinary food intake isn't a concern, high-dose supplements should be used cautiously.

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Biotin (Vitamin B7)

Involved in fat and carbohydrate metabolism, and well known for its association with hair and skin health.

Key functions

  • Acts as a coenzyme in several metabolic processes, including fatty acid synthesis and glucose production.
  • Associated with hair, skin, and nail health, which is why it's a common supplement ingredient for those purposes.

Possible deficiency symptoms

  • Deficiency is generally rare
  • Eating large amounts of raw egg white over a long period can cause deficiency, since a protein in raw egg white (avidin) blocks biotin absorption (hair loss, skin rash, etc.)

Key food sources

Egg yolk (cooked)Nuts, legumesSweet potatoes

Daily Value (DV): 30 mcg

Overdose cautions

No well-established overdose risk from food or typical supplement use has been reported for this vitamin.

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Folate (Vitamin B9)

Essential for DNA synthesis and cell division, and particularly important for fetal development in early pregnancy.

Key functions

  • Especially important for DNA/RNA synthesis and cell division in fast-dividing tissue such as blood and fetal tissue.
  • Involved in red blood cell production; deficiency can cause anemia.
  • Essential for the formation of the fetal neural tube (the origin of the brain and spinal cord) in early pregnancy.

Possible deficiency symptoms

  • Megaloblastic anemia (abnormally large red blood cells)
  • Deficiency during pregnancy raises the risk of neural tube defects (such as spina bifida) in the baby

Key food sources

Spinach, broccoli and other leafy greensLegumesAsparagusLiver

Daily Value (DV): 400 mcg DFE

Overdose cautions

No well-established overdose risk from food or typical supplement use has been reported for this vitamin.

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Vitamin B12 (Cobalamin)

Essential for red blood cell production and nervous system function, and naturally found only in animal foods.

Key functions

  • Works with folate in red blood cell production and DNA synthesis.
  • Needed to maintain the myelin sheath that insulates nerve cells.
  • Not naturally present in plant foods, so vegetarians and vegans need a deliberate intake plan.

Possible deficiency symptoms

  • Pernicious anemia (megaloblastic anemia)
  • Peripheral nerve problems like tingling in the hands/feet, and cognitive decline in severe cases
  • Strict vegans face a higher deficiency risk and are generally advised to supplement

Key food sources

Meat, fish, shellfishEggsMilk and dairy products

Daily Value (DV): 2.4 mcg

Overdose cautions

No well-established overdose risk from food or typical supplement use has been reported for this vitamin.

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Vitamin C (Ascorbic acid)

A powerful antioxidant that's essential for collagen synthesis and also helps iron absorption.

Key functions

  • An essential cofactor for synthesizing the collagen that makes up skin, blood vessels, and bone.
  • Acts as an antioxidant, protecting cells from damage by free radicals.
  • Improves absorption of plant-based iron (non-heme iron).
  • Also supports normal immune cell function.

Possible deficiency symptoms

  • Scurvy (bleeding gums, slow wound healing, fatigue) β€” rare today, but can occur with extreme, restrictive diets or malnutrition

Key food sources

Kiwi, strawberries, citrus fruitBell peppers, broccoli and other vegetablesPotatoes

Daily Value (DV): 90 mg

Overdose cautions

Being water-soluble, excess is mostly excreted in urine, but sustained high-dose intake above roughly 2,000 mg/day can raise the risk of digestive upset (diarrhea, cramping) and kidney stones.

What's the difference between fat-soluble and water-soluble vitamins?

Vitamins fall into two broad groups based on how the body absorbs and stores them.Fat-soluble vitamins (A, D, E, K) are absorbed along with dietary fat and can be stored in the liver and fatty tissue, so missing a day or two doesn't cause immediate deficiency β€” but sustained excess intake over a long period can build up in the body and cause toxicity.Water-soluble vitamins (the B-complex and vitamin C), by contrast, dissolve in water, are barely stored in the body, and any excess is excreted in urine β€” so they need to be taken consistently, but the risk of toxicity is comparatively lower.

Do I need to take vitamin supplements?

If you're eating a balanced diet, most vitamins can be obtained from food alone. That said, supplements are genuinely recommended in certain situations β€” for example vitamin D (if you get little sun exposure), vitamin B12 (if you follow a strict vegan diet), or folate (if you're planning a pregnancy or in early pregnancy). If you suspect a specific deficiency or are considering supplements, it's safer to check with a doctor or dietitian than to self-diagnose.

A note on this content

This page summarizes general nutrition information as educational content and is not a substitute for diagnosing or treating any specific condition, or for individualized nutrition advice. Deficiency-like symptoms can also be caused by conditions unrelated to vitamins, so if you notice concerning symptoms, please get a proper medical evaluation rather than self-diagnosing.

Frequently Asked Questions

Does taking more vitamins make you healthier?

No. Taking more than you need doesn't produce a proportionally bigger benefit. In particular, long-term high doses of fat-soluble vitamins (A, D, E, K) and some water-soluble ones (niacin, vitamin B6) can actually cause side effects, so it's best to take only what you need from supplements.

Is there a vitamin vegetarians and vegans should pay special attention to?

Vitamin B12 is the classic example. It's naturally found only in animal foods, so strict vegans face a higher deficiency risk and are generally advised to get it from fortified foods or a supplement.

Which vitamins matter more during pregnancy?

Folate (vitamin B9) is the best known β€” it's important for the fetus's neural tube development in early pregnancy, so supplementation is often recommended starting from the planning stage. Conversely, excess vitamin A can be risky for the fetus, so supplement use needs more caution during pregnancy. It's best to discuss an exact intake plan with your OB/GYN.