Rare Side Effects of 2,500 Micrograms of Sublingual Vitamin B12

Placing a B12 tablet under your tongue produces results similar to muscular injections with fewer complications. (Image: OksanaKiian/iStock/GettyImages)

Vitamin B12, cobalamin, plays an important role in human health and disease, and a deficiency in B12 can result in physical and mental health problems. Most people get the amount they need through supplements, but animal products like eggs and milk — and even some plants — also serve as good sources. Side effects from this water-soluble vitamin are rare, but it's been known to trigger the sometimes-fatal allergic reaction known as anaphylaxis, so speak with your doctor about it.

Tip

Even high doses of vitamin B12 are considered safe, and side effects are rare. There have, however, been cases of people experiencing the allergic reaction known as anaphylaxis after taking B12, underscoring the importance of talking to your doctor before including B12 in your health regimen.

Cobalamin Has Low Bioavailability

Some dietary cobalamin fails to reach your bloodstream. In fact, your ability to process cobalamin decreases as you increase your intake, so a large meal offers only slightly more cobalamin than a smaller meal. In addition, older adults often lose their ability to process cobalamin. All of this contributes to the likelihood of developing cobalamin deficiency.

Dietitians typically recommend getting 2.4 micrograms of cobalamin per day. However, some governments have increased this value to 8.6 micrograms. A person's gender, age and other factors affect these recommendations, and all values assume normal cobalamin processing.

Sublingual Cobalamin Offers Many Benefits

You can get cobalamin supplements in muscular and oral doses. The authors of a June 2016 report in the New Zealand Medical Journal noted the increasing popularity and many advantages of sublingual administration. Placing a B12 tablet under your tongue produces results similar to muscular injections with fewer complications.

A February 2018 paper in Clinical Nutrition also documented the effectiveness of sublingual administration. In this study, a weekly dose of 2,000 micrograms restored circulating cobalamin levels in patients with mild B12 deficiency. Interesting, daily doses of 50 micrograms had an even better effect.

Cobalamin Has Few Side Effects

Taking larger doses of cobalamin can help you overcome bioavailability issues, but whenever you consider upping your dose of a supplement, it's normal to have concerns about safety issues. Fortunately, the authors of a 2018 report in Food Fortification in a Globalized World concluded that even large doses of B12 remain safe, so 2,500 micrograms shouldn't pose a health problem.

Cobalamin Causes Allergic Reactions

While dose size doesn't matter, cobalamin can cause an allergic reaction, as reported in the May 2018 edition of Cureus. An older woman following a vegan diet for five years was prescribed a weekly 1,000-microgram injection of B12 and showed signs of anaphylaxis while receiving the second injection. A 2,000-microgram oral dose was prescribed, addressing the deficiency without side effects. The study noted that very few patients experience cobalamin-related anaphylaxis. Still, you should share any observed side effects with your doctor.

Cobalamin Comes From Many Sources

Because only microorganisms can make cobalamin, you have to get it from your diet or a supplement. Most animal products contain cobalamin. Farm animals offer you the best source of cobalamin, according to a February 2015 report in Nutrition Reviews. Organ meat has the greatest concentration of this vitamin. Dairy products contain considerably less. Vegetables rarely have cobalamin, but some edible seaweeds have it.

Traditional Cooking Changes Cobalamin Content

Food processing can have a dramatic effect on nutrients. For example, traditional cooking methods may cause a 62 percent decrease in cobalamin, according to a 2011 report in the Journal of Nutritional Science and Vitaminology. Modern techniques like vacuum-packed pouch cooking can eliminate this loss.

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