Vitamin B12 deficiency

Illustration of a capsule-shaped digital graphic representing Vitamin B12, with glowing circuitry and a bright center on the left side, and the label 'Vitamin B12' on the right side.

Vitamin B12 Deficiency: an overlooked concern in people without a colon or terminal ileum, such as those with a stoma or an ipouch.

Vitamin B12, also known as cobalamin, is an essential nutrient that plays a key role in red blood cell production, nerve function, and DNA synthesis. But for individuals without a colon and/or terminal ileum, such as those with an ileostomy, ileoanal pouch (ipouch), or urostomy, the risk of vitamin B12 deficiency is alarmingly under-recognised. While the general population may only occasionally hear about vitamin B12 in the context of tiredness or "energy boosters," for those living without certain sections of the gut, it can become a chronic, insidious deficiency, often difficult to detect and even harder to address without clinical awareness.

The Role of the Terminal Ileum

Vitamin B12 absorption occurs almost exclusively in the terminal ileum, the final portion of the small intestine. When the terminal ileum is surgically removed, as is often the case in individuals with inflammatory bowel disease, colorectal cancer, familial adenomatous polyposis, or other conditions requiring ileostomy or pouch formation, but also urostomy, B12 absorption may become severely compromised.

Just how common is B12 deficiency?

In the general population, vitamin B12 deficiency affects:

  • About 3% of people aged 20 to 40

  • Up to 20% of those aged 85 and older

However, studies suggest that 30% to 50% of individuals who have undergone surgeries involving the removal of the terminal ileum or colon may develop B12 deficiency, up to 15 times higher than the general population. That means a significant proportion of patients with ileostomies, ileoanal pouches (ipouches), urostomies may be quietly battling the effects of inadequate B12 absorption without even knowing it.

Chart listing signs and symptoms of vitamin B12 deficiency, including blurred vision, pale skin, irregular heartbeat, weak muscles, shortness of breath, anemia, fatigue, nerve problems, mood changes, memory loss, difficulty concentrating, loss of appetite.
An infographic about Vitamin B12 showing its function and role, including DNA synthesis, red blood cell formation, neurological health, and energy metabolism. Features a stylized illustration of a brain, a nerve, a DNA strand, a red blood cell, and a lightning bolt, with a yellow circle labeled "B12."
An infographic explaining how vitamin B12 is released by stomach acid, binds with Intrinsic Factor, and is absorbed in the terminal ileum, with illustrations of food, stomach, intestine, and a blood dish. The text reads: 'B12's Gourmet Trip! Released by stomach acid, binds with Intrinsic Factor. Absorbed in the terminal ileum. A well-orchestrated journey from plate to bloodstream!'
An educational graphic emphasizing the importance of getting vitamin B12 from animal foods such as fish, eggs, dairy, and cereals, featuring illustrations of a fish, eggs, cheese, and a B12 supplement box.
An infographic warning about early signs of vitamin B12 deficiency, including fatigue, weakness, anemia, tingling, and memory lapses. It features an illustration of a person looking sad, a stomach with HCl, a tongue, and intestines, with bold text emphasizing the importance of noticing symptoms early to save nerves and energy.

Common Signs and Symptoms

Because vitamin B12 deficiency can develop slowly over time, symptoms often go unrecognised or are attributed to other causes such as ageing, stress, or recovery from major surgery.

Importantly, many of these symptoms can occur even with “normal” B12 blood levels, which brings us to a critical point in diagnosis, where it becomes crucial for clinicians to pay attention to the signs and symptoms rather than the blood tests alone.

Blood Tests Do Not Tell the Whole Story

Standard blood tests measure serum B12 levels, but these tests can miss functional deficiencies, especially in people with chronic inflammation, altered gut anatomy, or malabsorption issues. Research has shown that symptoms may be present even when blood levels are above the conventional deficiency cut-off.

This presents a clinical challenge: should patients with symptoms be treated based on lab values or based on clinical judgment?

Some healthcare professionals are now adopting a symptom-based approach, recommending a therapeutic trial of vitamin B12 injections over a few months. If symptoms improve, it provides strong evidence that the deficiency was playing a role, regardless of baseline lab values. This advice is also in line with best practice, where this approach is now becoming largely recommended.

Suggested Treatment Approach (Based on Evidence-Based Practice)

Vitamin B12 deficiency anaemia is typically treated with hydroxocobalamin injections, given every other day for a few weeks or until symptoms improve. These are usually administered by a nurse. Once the initial phase is complete, ongoing treatment depends on the underlying cause and whether there are any neurological problems (e.g. blurred vision, pins and needles, memory problems, etc.). If it's due to diet, oral supplements may be offered; if it is caused by certain conditions, lifelong periodic injections are usually needed to maintain B12 levels and prevent relapse.

This protocol helps replenish body stores and maintain adequate B12 over time, especially in those who cannot rely on dietary absorption due to altered gut anatomy. If you are struggling with vitamin B12 deficiency and are struggling to get the right support, please contact us for advice.

Nutrition Matters Too: Dietary Sources of B12

While supplementation is critical in those with absorption challenges, understanding food sources of B12 is still important, especially for those at risk but not yet deficient

Animal-Based Sources

  • Organ meats: Liver (especially lamb liver), kidneys

  • Shellfish: Clams, mussels, oysters

  • Fish: Sardines, trout, salmon, herring

  • Beef: Beef liver, lean beef steak

  • Poultry: Chicken liver, turkey liver

  • Dairy: Milk, yoghurt, cheese (Swiss cheese)

  • Eggs: Hard-boiled eggs (especially the yolk)

Fortified Foods (for vegetarians and vegans)

  • Fortified cereals: Many breakfast cereals are fortified with B12

  • Nutritional yeast: Often fortified with B12

  • Non-dairy milk: Fortified almond, soy, rice milk

Clinical Insight: It is not just a nutrient; it is a neurological lifeline

One of the more distressing aspects of untreated B12 deficiency is permanent nerve damage. Tingling, numbness, and poor balance may become irreversible if not addressed early. What begins as mild fatigue or forgetfulness can evolve into debilitating neurological decline.

And because the onset is often so subtle, months or years may pass before patients, or even clinicians, recognise the connection. That is why proactive monitoring, early suspicion, and education are vital.

A Case for Routine Screening & Clinical Vigilance

Given the clear risk in patients with ileostomies, ipouches, or urostomies, some experts advocate for:

  • Annual symptom screening (regardless of B12 lab results)

  • Routine B12 testing at baseline and periodically thereafter

  • Low threshold for initiating treatment in symptomatic individuals

  • Trial of injections when levels are borderline or symptoms suggest deficiency

Final Thoughts: Bringing B12 Out of the Shadows

As healthcare providers, patients, and support teams, it is time to bring B12 to the forefront, not just on test reports, but in clinical conversations, patient education, and long-term care planning.

Because something as simple as a small injection or dietary tweak can mean the difference between fatigue and vitality, fog and clarity, isolation and thriving.