The B-complex vitamins -- niacin, thiamine, riboflavin, folate, biotin, pantothenic acid and vitamins B-6 and B-12 -- are essential for metabolism, forming healthy red blood cells, keeping your skin healthy and keeping your vision and nervous system functioning properly. They're readily available in many foods, so deficiencies in most of these vitamins aren't common in the United States, although some people may become deficient in folate or vitamins B-12 or B-6. Check with your doctor before taking a B-complex vitamin to make sure it would be safe for you.
Bioavailability and Absorption
Vitamins can come in a number of different forms, but one isn't necessarily better than the other. Although you would think that liquid forms were better absorbed because your body doesn't have to break them down as much, this isn't necessarily the case. For example, an April 2008 article on the Consumer Reports website notes that the body absorbs liquid and pill forms of vitamin B-12 equally well.
Amount of Vitamins
The B vitamins all work together for a healthy metabolism and to form ATP, which your body uses for energy. They're all needed in different amounts, however, so a supplement that provides equal amounts, such as 50 or 100 milligrams of each B vitamin, isn't well-balanced, and the extra B vitamins you're taking will just be excreted in your urine. It's usually best to choose supplements that contain no more than 100 percent of the daily value for any one vitamin. Getting too much niacin, for example, can cause heart palpitations and flushing.
Before choosing a vitamin B-12 supplement, check to see if it has the U.S. Pharmacopeia symbol on the package. If it says USP verified, this means it's been tested for contaminants, bioavailability and potency. It should have the amounts of each B vitamin that are listed on the label and it will have been manufactured using safe and sanitary practices.
Other Potential Considerations
Powdered vitamins can have a bitter aftertaste, and chewable versions of adult vitamins may not taste that great either, as they have to contain higher amounts of nutrients than children's versions. Liquid, powdered and chewable versions of vitamin B-12 may also be more expensive than pills. If you have difficulty swallowing, however, one of the non-pill versions of vitamin B-12 will be a better option for you. If you don't like the taste of the liquid or powder, you can try mixing it with juice or a smoothie.