Vitamin B12, also known as cobalamin, is an important water-soluble vitamin involved in red blood cell production, brain health and DNA synthesis ().
A deficiency in this key vitamin can cause serious symptoms, including fatigue, nerve damage, digestive issues and neurological problems like depression and memory loss ().
Therefore, many people turn to vitamin B12 supplements to help meet their needs and prevent a deficiency.
This article examines the main differences between methylcobalamin and cyanocobalamin — two of the most common sources of vitamin B12 found in supplements.
Vitamin B12 supplements are typically derived from two sources: cyanocobalamin or methylcobalamin.
Both are nearly identical and contain a cobalt ion surrounded by a corrin ring.
However, each have a different molecule attached to the cobalt ion. While methylcobalamin contains a methyl group, cyanocobalamin contains a cyanide molecule.
Cyanocobalamin is a synthetic form of vitamin B12 that is not found in nature ().
It’s used more frequently in supplements, as it’s considered more stable and cost-effective than other forms of vitamin B12.
When cyanocobalamin enters your body, it’s converted into either methylcobalamin or adenosylcobalamin, which are the two active forms of vitamin B12 in humans (4).
Summary Cyanocobalamin is a synthetic form of vitamin B12 found only in supplements, while methylcobalamin is a naturally occurring form that you can get through either food sources or supplements.
Another major difference between methylcobalamin and cyanocobalamin is the way they are absorbed and retained within your body.
Some studies suggest that your body may absorb cyanocobalamin better than methylcobalamin.
In fact, one study found that people’s bodies absorbed about 49% of a 1-mcg dose of cyanocobalamin, compared to 44% of the same dose of methylcobalamin ().
Conversely, another study comparing the two forms reported that about three times as much cyanocobalamin was excreted through urine, indicating that methylcobalamin may be retained better within your body ().
However, some research suggests that differences in bioavailability between the two forms may be insignificant and that absorption could be influenced by factors such as age and genetics (, ).
Unfortunately, recent research directly comparing these two forms of vitamin B12 is limited.
Additional studies are needed to measure the absorption and retention of methylcobalamin versus cyanocobalamin in healthy adults.
Summary Research shows that cyanocobalamin may be absorbed better in your body, while methylcobalamin likely has a higher retention rate. Other studies have found that the differences in absorption and retention are minimal.
When you ingest cyanocobalamin, it can be converted to both of the active forms of vitamin B12, methylcobalamin and adenosylcobalamin.
Much like methylcobalamin, adenosylcobalamin is essential to many aspects of your health.
It’s involved in the metabolism of fats and amino acids, as well as the formation of myelin, which creates a protective sheath around your nerve cells ().
Deficiencies in both forms of vitamin B12 can increase your risk of neurological issues and adverse side effects ().
But while supplementing with cyanocobalamin can increase levels of both active forms of vitamin B12, methylcobalamin doesn’t increase levels of adenosylcobalamin.
For this reason, it’s recommended to treat vitamin B12 deficiencies with either cyanocobalamin or a combination of methylcobalamin and adenosylcobalamin to ensure your body’s needs are being met ().
Summary Cyanocobalamin can be converted to both methylcobalamin and adenosylcobalamin. However, methylcobalamin supplements don’t increase levels of adenosylcobalamin.
Although distinct differences exist between methylcobalamin and cyanocobalamin, both have beneficial effects on health and can prevent B12 deficiencies ().
In fact, one study found that treating seven B12-deficient people with oral methylcobalamin normalized vitamin B12 levels in their blood within just two months ().
Similarly, another study showed that taking cyanocobalamin capsules for three months also increased vitamin B12 levels in 10 people with pernicious anemia, a condition caused by impaired B12 absorption ().
Both types of the vitamin may also provide other health benefits.
One review of seven studies showed that both methylcobalamin and a B-complex containing cyanocobalamin were effective in reducing symptoms of diabetic neuropathy, a complication of diabetes that leads to nerve damage ().
Additionally, several animal studies have found that each form could have neuroprotective effects and may be beneficial in treating conditions that affect your nervous system (,).
Summary Both methylcobalamin and cyanocobalamin can treat vitamin B12 deficiency. Animal and human studies have found that they could reduce symptoms of diabetic neuropathy and may have neuroprotective effects as well.
If you think you may have a vitamin B12 deficiency, talk to your doctor to determine the best course of treatment.
However, if you’re just looking to fill in the nutritional gaps in your diet, a vitamin B12 supplement may help.
Cyanocobalamin is a synthetic form of vitamin B12 that can be converted to the natural forms methylcobalamin and adenosylcobalamin.
The body may absorb cyanocobalamin better, while methylcobalamin has a higher retention rate.
Both can prevent B12 deficiency, but methylcobalamin should be combined with adenosylcobalamin for best results.