✨B12 Explained: Why It Gets So Much Attention✨

Vitamin B12 is one of the most frequently mentioned nutrients in wellness conversations — and one of the most frequently misunderstood. It appears on the ingredient lists of energy drinks, in the menus of IV clinics, and in the conversations of people who have been told their B12 is low and are trying to understand what that means.

This post is an honest look at what B12 actually does, why deficiency develops, who is most at risk, and what the investigation and management pathway looks like — including where injections and IV delivery sit in that picture.

What vitamin B12 is and what it does:
Vitamin B12 (cobalamin) is a water-soluble B vitamin that the human body cannot produce on its own — it must come from diet or supplementation. It is found naturally in animal products: meat, fish, dairy, and eggs. Plant-based sources of B12 are limited to certain fortified foods and some fermented products; strict plant-based diets carry a meaningful risk of deficiency without supplementation.

B12 is involved in several processes that matter considerably for day-to-day function. It is essential for the production of red blood cells — a deficiency can lead to megaloblastic anaemia, in which red blood cells become large and inefficient. It plays a central role in nerve function and myelin sheath maintenance — the protective coating around nerve fibers. And it is required for DNA synthesis and cell division.

This is why B12 deficiency can present with symptoms that seem varied and diffuse: fatigue, cognitive fog, tingling in the hands and feet, balance disturbances, and mood changes can all be associated with inadequate B12 status. These are significant symptoms — and they can develop gradually over months or years before a deficiency is identified.

Why deficiency develops:
B12 deficiency tends to develop through one of two main mechanisms: inadequate intake, or inadequate absorption.

Inadequate intake is most common in people following strict plant-based diets without supplementation or fortified foods. It can also occur in older adults who eat less overall.

Inadequate absorption is a more common driver in many clinical presentations. The absorption of B12 from food requires a protein called intrinsic factor, produced by the stomach lining. Conditions that reduce intrinsic factor production or damage the stomach lining — including autoimmune gastritis (which leads to pernicious anemia), long-term use of proton pump inhibitors or metformin, and certain gastrointestinal surgeries — can impair B12 absorption even when intake is adequate. This is clinically important: someone with an absorption problem who only takes oral B12 may not resolve their deficiency, because the problem is not getting the B12 in — it is absorbing it.

Who is most at risk in an Auckland context?

• People following vegan or strict vegetarian diets without reliable supplementation or fortified food intake
• Older adults — intrinsic factor production can decline with age
• People taking proton pump inhibitors (PPIs) long-term for acid reflux — widely prescribed in New Zealand
• People taking metformin for blood sugar management — metformin reduces B12 absorption over time
• Those with a history of gastrointestinal surgery
• People with autoimmune conditions affecting the stomach

B12 deficiency can also occur without obvious risk factors, which is why clinical testing is the only reliable way to assess status.

How deficiency is investigated
Serum B12 is the standard initial test, available through a GP or a clinic like Nandish. It is worth knowing that serum B12 can be in the "normal" range while active B12 deficiency exists — in some cases, a methylmalonic acid (MMA) or homocysteine test gives a more sensitive picture of functional B12 status. If you have symptoms that suggest B12 deficiency but a standard test comes back in range, this is worth discussing with your clinician.

Oral supplementation vs injection vs IV
This is where the clinical picture matters considerably.

For people with B12 deficiency caused by inadequate dietary intake and normal absorption capacity, high-dose oral B12 supplementation is often effective — at sufficient doses, a small percentage of B12 can be absorbed through passive diffusion even without intrinsic factor.

For people with absorption problems — including pernicious anemia — intramuscular (IM) injection or IV delivery bypasses the digestive system entirely and is typically the appropriate pathway. In New Zealand, B12 injections (hydroxycobalamin or cyanocobalamin) are commonly used in primary care for this purpose.

IV delivery of B12 as part of a broader nutrient infusion is something we discuss at Nandish in the context of each individual's situation. It is not automatically superior to injection; the right route depends on why the deficiency has developed and what the person's clinical needs are.

As with all nutrient-related conversations at Nandish: we test first, understand the cause, and then discuss the most appropriate pathway together.

What to do if you are concerned about your B12
If you are experiencing persistent fatigue, cognitive fog, or neurological symptoms — particularly if you follow a plant-based diet or take medications associated with reduced B12 absorption — it is worth investigating. A blood test is straightforward and gives you a baseline to work from.

We are happy to include B12 as part of a broader wellness assessment at Nandish. If you would like to have that conversation, our initial consultation is the right place to start.

The information in this article is general wellness education and is not medical advice. IV therapy at Nandish Health is provided following a consultation with a qualified clinician and is one of several options that may be considered as part of a broader wellness plan. Outcomes vary between individuals. Speak with your GP or one of our clinicians before starting any new therapy.

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