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Serious Side Effects of Vitamin B12?

Serious Side Effects of Vitamin B12?
Dr. Constance Odom, MD Picture of Dr. Constance Odom, MD

Medically reviewed by

Written by our editorial team.

Last Edited 6 min read

Vitamin B12 (also known as methylcobalmin) is often taken by individuals who suffer from certain kinds of anemias. It is often used by diabetics who are treating low blood sugar levels in some cases. Further, millions of Americans (and people around the world) suffer from Vitamin B12 deficiencies. So, how are these deficiencies cured? Some people choose to visit their doctor, who will administer a B12 shot during their office visit. But, an alternative is to take supplements in the form of pill or sublingual drops. Not only is this alternative far cheaper than a doctor's visit, you can readily order them online with several manufacturers. So, you can tackle the deficiency you are trying to treat, all while paying a much lower price for the solution.

As with any supplement or medication, many people who have to take, or are contemplating use of Vitamin B12 drops, wonder what the side effects are, and whether they are going to adversely interact with any medication or prescription being taken. The answer to these questions lie ahead.

What are the side effects I might experience?

Some people who take vitamin B12 supplements claim that they suffer from frequent headaches or migraines. Nervousness or anxiety are other side effects some individuals claim to suffer from when taking the supplement to treat a deficiency. Involuntary movement (or uncontrollable movements), itching, and swelling are sometimes complained of as well. These conditions however, are rare, and they typically come when individuals are taking higher dosage levels of the vitamin. Although they are not common, they are some things which should be noted. In the event you are taking the supplement, and find you suffer from these side effects, possibly speaking to your doctor will help you find a resolution to treating these side effects.

There are some more serious side effects which should also be noted, for those who are taking the vitamin to be aware of. In some cases, blood clots have occurred (again, this is typically with a very high dosage, and it is possibly a complication of other medical conditions, or other medications which interact adversely with the B12). Clots in the arms and legs, low potassium levels in the blood, allergic reactions (also typically linked to a preexisting allergy that you suffer from), or congestive heart failure, are some of the most serious side effects which can occur.

If you suffer from preexisting allergies, medical conditions, heart failure, or if you are taking other prescription medications (especially for heart conditions) it is highly important to discuss this with your doctor prior to taking B12 supplements. Not only to avoid these potential side effects, but also to ensure it is safe for you to take the sublingual drops, to treat the deficiency that you suffer from.


Read more about Vitamin B12:

Does everyone using supplements experience side effects?

Side effects are simply "warnings" of what can go wrong when you are taking a vitamin, or any other supplement or prescription medication. So, no, just because you are taking this vitamin does not mean you are going to suffer from any one of the side effects which are listed above. In fact, vitamin B12 is a water soluble vitamin. This basically means it is not going to have any potential toxic effects on your body or within the bloodstream.

Although side effects do occur with certain users, they are rare; and, when they are reported, the side effects typically resolve themselves within a few hours. Redness, itchiness, and other skin conditions, are typically due to high dosage levels of the vitamin, which can cause these conditions. And, the more serious side effects, such as blood clots or congestive heart failure, are likely to occur in individuals who are already treating a preexisting condition, have heart conditions, or in those who are genetically predisposed to these conditions. And, in terms of the allergic reactions, these are typically going to occur in individuals who suffer from allergies. In the event you do, speak to your doctor to learn of other preventive measures you can take, or if there is anything that can be done to treat the allergies, while you are taking the vitamin B12 supplement to treat your deficiencies.

Side effects are warnings. They are simply there to let you know what has happened to some users, and although they are extremely rare (and are typically not life threatening), there is always the possibility that something can go wrong. For such reasons, manufacturers must warn users, or those who are considering using their supplements, of the possibility that something of that nature can go wrong. For most users, you shouldn't worry about them, and it is typically safe for you to take vitamin B12 sublingual drops. Of course, if you are on other medications, or taking other vitamins and minerals to treat deficiencies, speak to your doctor to learn if it is safe to consume B12 with the other medications you are on.

Are supplements going to affect my overall health (negatively?)

Supplements are going to have an affect on your health, but they are likely positive, not negative. Read the above section which details complications, side effects, and use of the supplements, while you are taking other medications and supplements, to ensure it is safe to use Vitamin B12 supplements, together with those medications. Apart from that, it should have a positive impact on your health, which is to raise B12 levels. This will give you a jolt of energy, leave you feeling more energized, and help treat that lethargic feeling you have gotten so used to, during the day.

Treating a vitamin B12 deficiency is something which can be done very easily, with the use of a supplement. Vitamin B12 drops are easy, effective, and they are typically sufficient for treating deficiencies, with a majority of individuals who are suffering from low levels of the vitamin. There are side effects to familiarize yourself with, which are detailed above. With this being said, they are extremely rare, and supplements are typically going to have a positive impact, rather than negatively impact your health.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your physician about the risks and benefits of any treatment. Nu Image Medical may not offer the medications or services mentioned in this article.