There are eight B vitamins. Despite the numbering going up to B12, several numbers in between were dropped over the decades as scientists realized those substances didn’t meet the definition of a vitamin. The eight that remain are essential nutrients your body cannot make on its own (with a few partial exceptions), and they share a common job: acting as coenzymes that power the chemical reactions keeping you alive.
The Eight B Vitamins
Each B vitamin has both a number and a chemical name. Some are better known by one than the other.
- B1 (thiamin)
- B2 (riboflavin)
- B3 (niacin)
- B5 (pantothenic acid)
- B6 (pyridoxine)
- B7 (biotin)
- B9 (folate)
- B12 (cobalamin)
When you see a “B-complex” supplement on the shelf, it contains all eight of these in a single pill.
Why the Numbering Has Gaps
Early in the 20th century, scientists believed they had found a single water-soluble substance they called “vitamin B,” while fat-soluble compounds were grouped under “vitamin A.” It quickly became clear that “vitamin B” was actually a mixture of different compounds. As each one was isolated, it received the next number in the sequence.
Some of those numbered compounds, like B4, B8, and B10, were later reclassified. Either the body could produce them on its own or they turned out not to be essential nutrients at all. That left gaps in the numbering, which is why the list jumps from B3 to B5, from B7 to B9, and from B9 to B12. The convention stuck, and no one renumbered them.
What B Vitamins Do in Your Body
All eight B vitamins are coenzymes, meaning they act like on-switches for enzymes. Enzymes are proteins that speed up chemical reactions, but many of them can’t function without a coenzyme to activate them. Each B vitamin works on different enzymes, but the overarching theme is energy metabolism: converting carbohydrates, fats, and proteins from food into ATP, the form of energy your cells actually use.
Beyond energy production, individual B vitamins have specialized roles. Thiamin (B1) is central to converting food into ATP. Niacin (B3) also helps create and repair DNA. Pantothenic acid (B5) is used to build a compound that helps enzymes break down and build fatty acids. Folate (B9) and B12 both help form DNA and RNA, and B12 is critical for making healthy red blood cells.
Water Soluble, With One Exception
B vitamins dissolve in water. Your body uses what it needs and flushes the rest through urine, which is why you generally need a steady daily intake. You can’t stockpile most B vitamins the way you can fat-soluble vitamins like A or D.
B12 is the notable exception. Your liver stores it, and those reserves can last a few years. This means a B12 deficiency develops slowly, sometimes taking years of inadequate intake before symptoms appear. That’s a double-edged quality: it gives you a buffer, but it also means the problem can be well advanced before you notice anything wrong.
Folate vs. Folic Acid
These two terms both refer to vitamin B9, but they’re not identical. Folate is the natural form found in foods like leafy greens and legumes. Folic acid is the synthetic version used in supplements and fortified foods like bread and cereal. Your body absorbs folic acid more efficiently, at roughly 85% compared to about 50% for food-based folate. This is why folic acid fortification has been so effective at reducing certain birth defects, even in populations that eat plenty of vegetables.
What Deficiency Looks Like
Because B vitamins are involved in so many basic processes, running low on any of them can produce wide-ranging symptoms. Fatigue is the most common early sign across the board, since these vitamins are directly tied to energy production.
B12 deficiency is one of the most well-studied. It can cause a specific type of anemia where your body can’t produce enough healthy red blood cells. Beyond fatigue and weakness, B12 deficiency can lead to neurological problems: numbness or tingling in the hands and feet, difficulty with balance, and even cognitive changes like memory trouble or confusion. These neurological symptoms reflect peripheral neuropathy, where the nerves outside the brain and spinal cord become damaged. People who eat little or no animal products, older adults who absorb B12 less efficiently, and anyone with certain digestive conditions are at higher risk.
Severe B3 (niacin) deficiency causes pellagra, a condition historically associated with populations relying heavily on corn-based diets. It produces skin rashes, digestive problems, and mental disturbances. Pellagra is rare in developed countries today thanks to food fortification, but it still occurs in parts of the world where diets are limited.
Where to Find Them in Food
No single food delivers all eight B vitamins in large amounts, which is why a varied diet matters. Animal products, particularly meat, fish, eggs, and dairy, are the richest sources overall. Liver is especially dense in nearly every B vitamin. Whole grains provide thiamin, niacin, and B6. Legumes and leafy greens are strong sources of folate. Nuts, seeds, and avocados contribute pantothenic acid and B6.
B12 stands out because it is found almost exclusively in animal-derived foods: meat, fish, shellfish, dairy, and eggs. This makes it the B vitamin most likely to be low in people following a vegan diet. Fortified plant milks, nutritional yeast, and supplements can fill the gap, but it requires deliberate planning.
Many countries also mandate fortification of staple foods. In the U.S. and U.K., flour and cereals are commonly fortified with folic acid, thiamin, niacin, and riboflavin, which has significantly reduced deficiency rates at the population level.