Is it ok to take 1000 mcg of vitamin B12 a day?

There is no risk of an overdose when taking large amounts of vitamin B-12 such as 1000 mcg, because it is a water-soluble vitamin. Meaning the body will use the amount that it needs then the excess will be excreted through urine.

Vitamins are organic nutrients that are highly essential for maintaining growth, reproduction and various metabolic functions in our body, therefore vitamins are required to be present in our diet.

Vitamin B is a class of water-soluble vitamins consisting of eight members (Vit B1, B2, B3, B5, B6, B7, B9 and B12) which together are referred to as B complex. Vitamin B12 is a vital nutrient required to produce red blood cells, regulate the formation of myelin sheaths that shield the nerve cells of the nervous system and facilitate the synthesis of DNA.

Of note, vitamin B12 helps in the prevention of pernicious anemia, hence, it is otherwise known as “anti-pernicious anemia factor”. Vitamin B12 acts as a cofactor in two enzymes such as methionine synthase and methylmalonyl-coenzyme A mutase, which are critical enzymes in the production of SAMe (or S-adenosyl methionine), hemoglobin and catalytic intermediate by-products involved in fat and protein metabolism.

Vitamin B12 exists in four different forms, 3 bioactive and easily absorbed forms (methylcobalamin, adenosylcobalamin, and hydroxocobalamin) and 1 not so easily absorbed. All of these forms contain cobalt metal atoms and thus collectively are referred to as cobalamins.

Cobalamin consists of a heme-like planar corrin ring structure where four pyrrole nitrogens are coordinated to the central cobalt atom. Methylcobalamin occurs naturally in the body and assists in producing red blood cells, DNA and takes part in other physiologic functions. It is found in injections and oral supplements of vitamin B12.

Adenosylcobalamin, an unstable molecule, exists naturally, is required for energy metabolism, and is hard to find in vitamin B12 supplements.

Another natural form of vitamin B12 is hydroxocobalamin (or hydroxocobalamin), it’s considered the most well-tolerated form of all the cobalamins.

It is produced by the bacteria present in the digestive tract and is also available in both injectable and oral forms. Hydroxycobalamin is readily converted into the active forms, adenosylcobalamin, and methylcobalamin, inside the body.

Many have genetic mutations like MTR (methionine synthase) and MTRR (methionine synthase reductase) genetic variants who can’t make this conversion very well and it affects the absorption of cobalamin in the body.

Cyanocobalamin is cheap and the most common form of B12 found in oral, intramuscular, and intravenous vitamin B12 supplements.

Vitamin B12 is scarcely available in a vegetarian diet. Many bacteria and algae can synthesize cobalamins whereas plants do not absorb cobalamins from the soil and thus, there is little or no vitamin B12 in vegetable sources.

The presence of vitamin B12 is low in milk, dairy and soy products, so they must be consumed in large quantities to meet the daily requirement. Fortified foods are another way to get a source of vitamin B12 into one’s diet (however, it will be almost exclusively in the cyanocobalamin form, which is not well absorbed by most people).

And if we know anything in this day and age, it’s that a large majority of people have ‘gut dysbiosis’. Therefore, absorbing B12 can be almost impossible through the gut for many (especially for those who have genetic complications as well). This is why doctors recommend oral/sublingual routes with ‘active cobalamins’ – that way the mucous membrane under the tongue is leveraged as one of the most optimal ways to absorb cobalamin.