Is Vitamin B12 Bad for You? Risks and Precautions

For most people, vitamin B12 is not bad for you: it is a water-soluble vitamin and any excess is excreted in urine. The known problems arise mainly from the opposite side — from a lack of B12, which can cause haematological and neurological changes ¹ — and not from a one-off excess. That said, "safe for most" is not the same as "harmless for everyone": there are groups and situations where supplementation calls for caution and professional supervision.

This article explains what the evidence shows about the safety of B12, who is most at risk of deficiency, which medicines interfere with its absorption, what the labels of TuttiBear gummies say and when you should seek advice from a healthcare professional.

Is vitamin B12 bad for you at high doses?

Vitamin B12 is water-soluble and the body regulates its absorption relatively efficiently: when the dose is high, a smaller percentage is absorbed and the rest is excreted. That is why, unlike fat-soluble vitamins such as A or D, no tolerable upper intake level has been set for B12 in healthy adults.

This does not mean that very high doses are always harmless. In a clinical setting, high parenteral doses are given in specific situations and the adverse effects described are generally mild and reversible ². But that context — administration by injection, in patients — does not translate directly to a gummy taken at home by a healthy person. The practical conclusion is simple: in healthy people, oral B12 supplementation at the usual doses found in supplements is not associated with relevant adverse effects, but that does not justify taking arbitrarily high doses without need.

Who is most at risk of B12 deficiency (and not the opposite)?

The clinical risk associated with B12 is almost always that of deficiency, not excess. B12 deficiency and insufficiency can cause haematological and neurological problems, and there are factors unrelated to disease that increase this risk: dietary habits, food processing and preparation, lower bioavailability, increased physiological needs and iatrogenic factors such as medicines or surgery ¹.

According to that review, the groups at highest risk include vegans, vegetarians, older adults, people on restricted diets, breastfed and premature infants, and those who take certain medicines or have undergone certain surgeries ¹. A 2024 meta-analysis that assessed functional B12 status in adult vegans concluded that a vegan diet without supplementation is associated with lower serum B12 values and higher levels of total homocysteine, markers of functional deficiency ³.

If you recognise yourself in one of these groups, the relevant question is not "is B12 bad for me?" but "am I deficient and do I need to supplement?". That assessment is made with blood tests and a healthcare professional.

What side effects can appear with oral supplementation?

At the usual doses of oral supplements, the effects reported are infrequent and generally mild. The review on the use of B12 in intensive care describes that even high parenteral doses are associated with mild and reversible side effects ².

In practice, what people notice most often is not an adverse effect but more intensely coloured urine — a consequence of excreting the excess water-soluble vitamin. It is not a sign of a problem.

If you feel gastrointestinal discomfort or another symptom you attribute to the supplement, the reasonable approach is to stop and speak to a healthcare professional, especially if the symptoms persist or are intense.

If you feel any discomfort, you can try taking the supplement with a meal, which often reduces the feeling of unease. If the symptoms persist or are intense, stop and speak to a healthcare professional.

Interactions and situations that need attention

B12 does not interact with medicines in the same way that many drugs interact with each other, but there are situations in which its absorption or its levels can be affected.

Medicines that reduce stomach acid

Proton pump inhibitors are one of the most widely used classes of medicines and have a favourable safety profile, but long-term use has been studied for its effect on nutrient absorption. A review on the subject concluded that, although studies in this area have divergent conclusions, consistent results from several studies support a long-term adverse effect on the absorption of vitamin B12, iron and magnesium ⁴. This does not mean that all users become deficient, but it justifies monitoring, especially with prolonged use.

Metformin and other medicines

The review on risk factors unrelated to disease explicitly includes iatrogenic factors linked to the use of medicines or to surgery as causes of B12 insufficiency ¹. If you take long-term medication — for diabetes, for the stomach, anticonvulsants or others — the decision to supplement should be discussed with your doctor, who can assess whether it makes sense to measure your levels.

In addition to proton pump inhibitors and metformin, other medicines can interfere with B12, such as some antibiotics (for example, neomycin), anticonvulsants (phenytoin, phenobarbital) and colchicine, used for gout. This is not an exhaustive list and the clinical relevance varies from case to case, but if you take long-term medication, tell your doctor before adding a supplement.

Pregnancy and breastfeeding

B12 deficiency is a relevant public health problem, with a greater burden in older adults, pregnant women and young children ⁵. A Cochrane review assessed the benefits and risks of oral B12 supplementation during pregnancy, but the available data do not allow firm conclusions on all outcomes ⁵. In pregnancy and breastfeeding, any supplementation should be decided with a healthcare professional — never on your own initiative.

Kidney or liver disease

There is no evidence that oral B12 at usual doses causes liver or kidney damage in healthy people. Even so, in people with a diagnosed disease, the assessment of need and dose should be made by a doctor, because the clinical context changes what is appropriate.

In people with an allergy or sensitivity to cobalamin or to any component of the supplement, supplementation should be avoided. Allergic reactions, although rare, can be severe and require medical assessment.

What the labels of TuttiBear gummies say

If you are looking for B12 in a gummy, it is worth understanding that the amount per serving varies widely between products. The following table summarises the vitamin B12 values in the products in the range that include it, exactly as they appear on the label:

Product	Serving	Vitamin B12 per serving	% NRV
Multivitamin Gummies	2 gummies	8 µg	320%
Hair & Nails Gummies	2 gummies	6 µg	240%
Appetite Control Gummies	2 gummies	2.4 µg	96%
Energy Gummies with Guarana	2 gummies	10 µg	400%
Creatine Gummies	3 gummies	50 µg	2000%
Focus and Concentration Gummies	2 gummies	500 µg (methylcobalamin)	20000%
Stress Relief Gummies	2 gummies	500 µg	20000%
Children's Multivitamin Gummies (from 2 years)	1 gummy	3 µg	120%

As you can see, most products provide B12 in micrograms, well above the daily reference requirement, which is common in supplements and is not in itself a safety problem. The gummies intended for children from 2 years provide 3 µg per gummy and should be given under adult supervision, as stated on the label. In any case, do not exceed the daily dose recommended on the label and remember that doses used in studies are not instructions for taking.

The gummies contain sugar or sweeteners, an aspect that is relevant for anyone with diabetes or who is managing their weight — always check the label. Because they are chewed, they can also be a problem for anyone with dental braces, and the sugar can contribute to tooth decay if oral hygiene is not careful. Keep the gummies out of reach of children: they can look like sweets and a child who eats several may ingest a dose well above the recommended one. If that happens, contact your doctor, your pharmacist or your country's poisons information centre.

B12 gummies: are there safety differences compared with tablets?

There are no studies directly comparing the safety of gummies with that of B12 tablets — that comparison simply does not exist in the literature. What is known is that the oral route is effective: a clinical evidence-based analysis concluded that oral supplementation is as effective as intramuscular injections in patients with confirmed B12 deficiency, and a Canadian economic analysis estimated the cost savings of that change ⁶. A 2024 network meta-analysis, which included 13 studies and 4,275 patients, compared the oral, intramuscular and sublingual routes and found no statistically significant differences between them in terms of raising B12 and haemoglobin levels, although the authors note that the limited number of studies may have contributed to the lack of significance ⁷.

In other words: the available evidence tells us that the oral route works, but it does not allow us to state that a gummy is better or worse than a tablet. If you have absorption difficulties due to coeliac disease, gastric surgery or another condition, that is a conversation to have with your doctor, because the pharmaceutical form may not be the decisive factor. To go deeper, see the comparison between gummies and tablets.

Common myths about B12

• "B12 gives you energy." B12 is essential for DNA synthesis and for cellular energy production ⁸. It is not a stimulant: if your levels are normal, supplementation does not produce a noticeable energy effect.
• "More is always better." There is no evidence of additional benefit in taking doses well above your needs when there is no deficiency. The excess is excreted.
• "B12 is bad for the liver." There is no evidence that oral B12 at usual doses causes liver damage in healthy people. At high parenteral doses, the effects described are mild and reversible ².
• "B12 prevents neurodegenerative diseases." Subclinical deficiency has long-term consequences that are not yet fully known and may include adverse effects in pregnancy and on vascular, cognitive, bone and eye health ⁸. There is no basis for stating that supplementing prevents dementia.
• "Because it is a vitamin, it is harmless to everyone." B12 is safe for most people, but there are groups — pregnant women, children, people with kidney or liver disease, those taking certain medicines — in which the decision should go through a healthcare professional.

When to talk to a healthcare professional

You should consult a doctor or pharmacist before starting or continuing B12 supplementation if:

• You are pregnant, breastfeeding or planning to become pregnant ⁵.
• You have a young child and are thinking of supplementing them — the decision belongs to the paediatrician.
• You take long-term medication, especially proton pump inhibitors, metformin or anticonvulsants — consult your doctor ^{4 1}.
• You have kidney or liver disease or another diagnosed condition.
• You follow a vegan or vegetarian diet and have never had your B12 tested ³.
• You feel neurological symptoms such as tingling or numbness in your hands and feet — these may indicate B12 deficiency and require medical assessment ¹.

Seek immediate medical help if you experience allergic reactions such as skin rash, itching, swelling of the face or difficulty breathing, palpitations or irregular heartbeats, severe or persistent headaches, nausea or vomiting that does not stop, or tingling and numbness in your hands and feet. These signs are rare, but if they occur, stop the supplement and contact a healthcare professional.

If you belong to a group at risk of deficiency, supplementation may be necessary — but the dose and the form should be guided by someone who knows your case. If you do not belong to any risk group and have a varied diet, you probably do not need to supplement. To understand the role of B12 in the body, see how vitamin B12 works and the real benefits of B12.

What we still do not know

The evidence on the long-term safety of high doses of B12 in healthy people is limited. The review on subclinical deficiency notes that the long-term consequences of this condition are not fully known and may include adverse effects in pregnancy and on vascular, cognitive, bone and eye health ⁸. This means that caution should go both ways: neither ignore a deficiency nor supplement in excess without reason.

The interaction between B12 and folate is complex and not yet fully understood, which reinforces the importance of a professional assessment before making decisions based only on symptoms or on information found online.

In summary: for most people, vitamin B12 is not bad for you. But the complete answer to the question "is it bad for you?" depends on who is taking it, at what dose and why — and that assessment, when there are doubts, belongs to a healthcare professional. If you want to know more about the right dose, see the guide to the recommended daily dose of B12 and the ingredient page for vitamin B12.

Frequently asked questions

Is vitamin B12 bad for your kidneys?

There is no evidence that oral vitamin B12 at usual doses causes kidney damage in healthy people. In people with a diagnosed kidney disease, the assessment of need and dose should be made by a doctor, because the clinical context changes what is appropriate.

Can I take vitamin B12 every day?

Yes, at the doses stated on the supplement label. B12 is water-soluble and the excess is excreted in urine. You should not exceed the daily dose recommended on the label or take high doses without a clear reason and without professional guidance.

Does vitamin B12 make you gain weight or give you energy?

No. B12 does not provide energy directly and has no calories. It is essential for DNA synthesis and cellular metabolism, but if your levels are normal, supplementation does not produce a noticeable energy effect.

Who should not take vitamin B12 supplements?

People with an allergy to any component of the supplement should avoid it. Pregnant women, breastfeeding women, children, people with kidney or liver disease and anyone taking long-term medication should speak to a healthcare professional before supplementing.

Does vitamin B12 interfere with blood tests?

Biotin, often present in multivitamin supplements, can interfere with the results of some laboratory tests. If you take a supplement that contains it, tell your doctor and the laboratory before having any tests.

Are vitamin B12 gummies as safe as tablets?

There are no studies directly comparing the safety of gummies with that of B12 tablets. What the evidence shows is that the oral route is effective and comparable to intramuscular injections in people with confirmed deficiency. Choosing the form is mainly a matter of preference and convenience.