Vitamin B12 Vs. B Complex: Which Is Best?

While most vitamins and minerals have just one nutrient to their name (like vitamin C or calcium, for example), the B vitamins are a bit more nuanced.

With eight vitamins comprising the B complex family, it can get confusing to figure out what exactly each of them does—and how they are similar or different. 

Most notably, people wonder whether they should take an entire vitamin B complex supplement or solely vitamin B12. 

The short (and annoying) answer is: it depends. But not to worry, we’ll break it down for you in this article all about the differences between vitamin B12 and B complex supplements and the best scenarios to take each in.

Vitamin B12 vs. B Complex

B vitamins are essential for human health, with benefits ranging from cellular function and cognition to mood and migraines. But while they tend to have some overlapping actions, their functions can also vary widely—let’s take a closer look.

What Is Vitamin B12?

Vitamin B12 is a water-soluble vitamin needed for healthy red blood cell formation and DNA production. 

Most people refer to B12 as “cobalamin,” although there are several different forms, including methylcobalamin and 5-deoxy-adenosylcobalamin (the metabolically active versions), hydroxocobalamin, and cyanocobalamin.

In addition to DNA synthesis, B12 is vital for energy production, as it acts as a cofactor for certain enzymes involved in cellular energy metabolism in the mitochondria.

For the biochemistry nerds out there, B12 acts as a cofactor to convert methylmalonyl-CoA to succinyl-CoA—a compound that participates in the Krebs cycle to produce energy in the form of ATP by metabolizing food. 

B12 plays a role in the brain and nervous system, as it’s required for nerve development, myelination, and function. (Myelination refers to the addition of a fatty sheath surrounding nerve fibers to improve the rate of signal conduction between neurons.) 

It is also needed to convert the amino acid homocysteine into methionine. Homocysteine is an amino acid that, when elevated, increases the risk of dementia, heart disease, and stroke, so lowering its levels via this conversion is beneficial.

Benefits of Taking B12

Vitamin B12 supplements may benefit the following areas (although research on some is limited and inconclusive): 

• Energy production and fighting fatigue. The leading reasons why people take B12 supplements are for energy and fighting fatigue. However, it may only work if you are deficient or inadequate in vitamin B12 or have a chronic health condition, like myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or megaloblastic anemia (see next point).
• Reduced risk of megaloblastic anemia. B12 deficiency causes megaloblastic anemia, a condition causing dysfunctional and abnormally shaped red blood cells. Without enough healthy and functional red blood cells, your tissues and organs don’t get enough oxygen, causing weakness, fatigue, shortness of breath, tingling in the extremities, and trouble walking. Therefore, taking B12 in these cases can boost energy by allowing for the proper flow of oxygen and nutrients to all tissues of the body.
• Brain function and memory. Vitamin B12 may support brain health, as research shows that having blood vitamin B12 levels on the low side of normal is linked to poor memory performance. However, clinical trials have not always supported the cognitive benefits of supplementing with B12—especially in healthy people.
• Cardiovascular health. B12 is thought to support cardiovascular health by reducing homocysteine levels. However, while vitamin B12 deficiency is associated with an increased risk of heart disease in some cases, vitamin supplementation trials have not shown the same benefits.
• Nerve regeneration and repair. B12 supports healthy nerve function by protecting nerve cells from damage, promoting myelin formation, and reducing Wallerian degeneration responses—nerve degeneration after a nerve fiber is injured or crushed. B12 (when taken with dexamethasone, an anti-inflammatory steroid medication) has also been shown to increase the activity of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), which promote nerve survival and regeneration. 
• Reducing nerve pain. Research suggests that the potential mechanism behind B12’s ability to alleviate pain is through increasing nerve regeneration and decreasing ectopic nerve firing (which causes neuropathic pain).
• Improving symptoms of diabetic neuropathy. B12 may also help with diabetic neuropathy—a complication that comes from uncontrolled high blood sugar levels. Over time, high blood glucose damages the small blood vessels that supply nerves, so nutrients and oxygen cannot reach the nerves. This causes nerve damage, leading to pain, tingling, and numbness. In one study, people with diabetic neuropathy who took 1,000mcg of B12 for one year had significant improvements in all neurophysiological parameters, sudomotor function (sweat gland activity), pain scores, and quality of life.

What Are the B Complex Vitamins?

Vitamin B complex is a term encompassing the eight B vitamins:

• Vitamin B1 (thiamin): Thiamin is vital for energy metabolism, as it plays a significant role in the Krebs cycle—a series of steps called aerobic respiration by which our cells produce energy from food.
• Vitamin B2 (riboflavin): Riboflavin acts as a cofactor to help metabolize carbs, fat, and protein into cellular energy. It has also been found to function as an antioxidant, supporting skin health and immune function.
• Vitamin B3 (niacin): Niacin is also needed for energy metabolism as it is a precursor to NAD+, a coenzyme required by every one of our cells for energy production, mitochondrial health, and DNA repair. It also helps with healthy nerve function.
• Vitamin B5 (pantothenic acid): Pantothenic acid is involved with cellular energy metabolism and synthesizing the neurotransmitter acetylcholine, which is involved with muscle contraction, memory, motivation, and learning.
• Vitamin B6 (pyridoxine): B6 helps with cognition, mood, immunity, nerve function, and the breakdown of carbohydrates, proteins, and fats. It also helps convert homocysteine into methionine. 
• Vitamin B7 (biotin): Biotin is essential for healthy hair, nails, and nerve function. It also is involved with gene regulation, cell signaling, and promoting the metabolism of fatty acids, glucose, and amino acids. 
• Vitamin B9 (folate or folic acid): Folate is crucial for fetal development, as it prevents neural tube defects like spina bifida. It’s also needed for DNA repair, the formation of new red blood cells, and converting homocysteine to methionine. 
• Vitamin B12 (cobalamin): B12 is needed to form healthy red blood cells and DNA and plays a role in the brain and nervous system. 

Benefits of Taking Vitamin B Complex

Taking a B complex supplement with all eight B vitamins has many potential health benefits, including the previously mentioned advantages of B12.

Vitamin B complex supplement benefits may include:

• Improved energy and reduced fatigue. As all of the B vitamins (except folate) play a vital role in energy metabolism, supplementing with B complex vitamins may help improve energy—but likely only if you lack one of the B vitamins. However, even subclinical inadequate levels (meaning yet to be diagnosable or evident on lab testing) of some B vitamins may cause fatigue or low energy.
• Improved athletic performance. Some research has found that supplementing with B vitamins improves energy in athletic situations. For example, a small study of ultra-marathon runners found that those who took riboflavin supplements had faster times and quicker muscle recovery than those who took a placebo. 
• Improved mood. Several B vitamins, especially B6, B9, and B12, are associated with mood improvements. In a review of 18 studies, eleven trials reported a positive effect of B vitamins on improving overall mood or a facet of mood, with the most significant benefits to stress. As high homocysteine is a risk factor for depression and low mood, lowering homocysteine with these B vitamins may be the link.
• Protection against cognitive decline. Similarly, B6, B9, and B12 could be associated with brain health due to their role in lowering homocysteine. In a meta-analysis of 95 studies with 46,175 participants, people without dementia who took B vitamins had significantly lower rates of developing cognitive decline. 
• Reduced risk of megaloblastic anemia. Like with B12, folate deficiency can also cause megaloblastic anemia. Taking a supplement containing both of these B vitamins can be beneficial if you don’t know which one is causing the anemia. 
• Reductions in migraine episodes and severity. Vitamins B6, B9, and B12 may also be able to prevent migraine episodes or reduce their severity, although the research is limited. One study found that people with migraine with aura (one that causes sensory disturbances like vision changes, blind spots, or flashes of light) who took B vitamin supplements with B6, B9, and B12 had reductions in migraine-related disability from 60% to 30%. Other research found B1, B6, and B12 supplements reduced the severity of menstrual-related migraine attacks. 
• Reductions in nerve pain or neuropathy. Vitamins B1, B6, and B12 are considered the “neurotropic B vitamins,” meaning they benefit the central nervous system. These B vitamins protect nerves against oxidative stress and damage, maintain myelin health, promote nerve cell survival, provide essential energy to nerve cells, and more. Conversely, B1, B6, or B12 deficiencies are linked to nerve degeneration, pain, and neuropathy.

Who Should Take B12 Supplements?

While every case is different, the following groups of people could consider taking B12 supplements:

• Vegans, vegetarians, and pescatarians. Vitamin B12 is only naturally found in animal products, so vegans need to take supplemental B12. Vegetarians and pescatarians may also want to supplement with B12, depending on their average intake of animal foods or foods fortified with B12. 
• People looking for an acute energy boost. High doses of B12 are thought to support cellular energy production, which may provide a short-term energy boost. This is why high amounts of B12 are present in certain energy drinks or shots. However, the energy boost may only work in deficient people or those with certain health conditions. 
• People with vitamin B12 deficiencies or megaloblastic anemia from B12 deficiency. Megaloblastic anemia is caused by either B12 or folate deficiency, leading to abnormally large and oval-shaped red blood cells. Without enough healthy and functional red blood cells, your tissues and organs don’t get enough oxygen, causing weakness, fatigue, shortness of breath, tingling in the extremities, and trouble walking. In this case, your doctor may recommend extra-high doses of B12 to correct the deficiency.   
• Older adults: The capacity to absorb vitamin B12 from food or supplements decreases in older adults because of declines in stomach acid production, which is needed to absorb B12. 
• People on certain medications: Some medications can interfere with the absorption or metabolism of vitamin B12, including proton pump inhibitors (PPI), metformin, nitrous oxide anesthesia, some epileptic medications, and colchicine (for gout).
• People with gut absorption issues. People with problems absorbing nutrients due to Crohn’s or inflammatory bowel disease, celiac disease, pancreatic disease, or weight loss surgery may need to take B12 in different forms that bypass the gut, like injections or sublingual (under the tongue) supplements.

Vitamin B Recommended Dosage and Upper Limit

The Food and Nutrition Board has set either an RDA (Recommended Dietary Allowance) or AI (Adequate Intake) for vitamins and minerals.

The RDA is the average daily nutrient intake level needed to meet the requirements of 97-98% of healthy people. The AI level is assumed to be nutritionally adequate for most people, but the available evidence is insufficient to develop an RDA.

For all the B vitamins, there are established RDAs or AIs for adult males and females: 

The Bottom Line: Should You Take B12 or B Complex?

Vitamin B12 and the B complex vitamins both have their own set of health benefits. While B12 is included in the B vitamin complex, some people may need or want a solo B12 supplement, which typically contains higher doses of B12.

B12 is linked to improved energy levels (possibly only in deficient people or those with anemia or chronic fatigue), cognitive function, heart health, and nerve repair or neuropathy reduction.

Many groups of people need to take B12 supplements, including vegans or vegetarians, older adults, those taking certain medications, and people with gut absorption issues.   

However, the full B vitamin complex contains seven other vitamins that can benefit health above and beyond what B12 can do on its own—plus, some of the B vitamins work synergistically.

Taken together, the B vitamins are linked to improved energy, cellular health, anemia prevention, neurological health (including cognition, mood, and migraine relief), and reductions in nerve pain or neuropathy.

B12 and B Complex FAQs