Vitamin B12 deficiency over 60 affects approximately 20% of elderly individuals, with prevalence rising to 40% in some populations. This widespread deficiency has serious implications, especially when it comes to cognitive health. Evidence reveals a strong connection between b12 deficiency in elderly populations and conditions like mild cognitive impairment and dementia. Symptoms of b12 deficiency in elderly individuals can mimic dementia itself. This raises critical questions about what causes b12 deficiency in older adults and whether b12 deficiency memory loss is reversible. This piece gets into the causes, symptoms, diagnosis, and treatment strategies for B12 deficiency after 60.
Understanding Vitamin B12 and its role after 60
Image Source: Medical News Today
What is Vitamin B12
Vitamin B12, known scientifically as cobalamin, represents an essential nutrient that the body cannot manufacture on its own. The name "cobalamin" derives from the mineral cobalt at the centre of its molecular structure [1]. Two metabolically active forms perform the actual work in human cells: methylcobalamin and 5-deoxyadenosylcobalamin [2][3]. These compounds function as cofactors for critical enzymes that keep cellular machinery running smoothly.
Methionine synthase and mitochondrial methylmalonyl-CoA mutase depend entirely on B12 to catalyse their reactions [2]. The first enzyme converts homocysteine to methionine, an essential amino acid that serves as a building block for S-adenosylmethionine [3][3]. This methyl donor participates in nearly 100 different biochemical processes that include DNA synthesis, RNA formation and protein modification [3]. The second enzyme metabolises propionate, a short-chain fatty acid, and converts methylmalonyl-CoA to succinyl-CoA [3][3]. These pathways malfunction without adequate B12 and cause oxidative stress and impaired mitochondrial function [2].
B12 holds unique importance for the nervous system, red blood cell formation and DNA synthesis [3]. The vitamin supports myelination of nerve fibres and ensures proper central nervous system development [3]. Like how B vitamins for testosterone work together to support hormonal balance, B12 cooperates with folate in one-carbon metabolism to maintain cellular health.
Why B12 becomes critical after age 60
Age fundamentally alters the body's relationship with B12. Between 10% and 30% of adults over 50 struggle to absorb B12 from food [4][5]. The stomach produces less hydrochloric acid with advancing years and hampers the release of B12 from protein-bound forms in meat, fish and dairy products [5]. Atrophic gastritis, a chronic age-associated stomach inflammation, afflicts up to 30% of adults over 51 and further reduces gastric acid secretion necessary for B12 liberation [2][3].
The small intestine and kidneys also become less efficient at B12 processing. Receptor expression for the B12-intrinsic factor complex decreases in enterocytes and kidney cells, which lowers absorption and renal reabsorption rates [6]. Older individuals experience declining B12 availability even when dietary intake appears adequate for that reason.
Brain tissue reveals concerning changes. Older subjects show lower levels of methylcobalamin and adenosylcobalamin in brain cells despite normal B12 levels in blood [2]. This discrepancy indicates deterioration in B12 import into cells and its conversion to active forms. DNA methylation in the nervous system, which associates strongly with memory formation and learning, declines with age [2]. The body stores approximately 1 to 5 milligrammes of B12, mostly in the liver (60%) and muscles (30%), but loses 0.1% to 0.2% of this pool daily [3][2]. Symptoms of vitamin b12 deficiency in elderly populations can take several years to surface because of these substantial reserves [3].
How your body processes B12
B12 absorption follows an intricate pathway with multiple organs and proteins. Food-bound B12 first requires liberation in the mouth, where saliva containing haptocorrin protein begins the extraction process [3][7]. Hydrochloric acid and pepsin in the stomach complete the separation and free B12 from its protein matrix [3][3]. The freed vitamin then binds to haptocorrin for transport through the stomach [3][2].
Pancreatic enzymes degrade haptocorrin in the duodenum and release B12 to bind with intrinsic factor, a protein secreted by stomach parietal cells [3][2]. This B12-intrinsic factor complex travels to the distal ileum, where specialised receptors (cubilin and amnionless) aid absorption through receptor-mediated endocytosis [3][2]. Roughly half of ingested B12 absorbs in healthy adults [5]. Passive diffusion accounts for 1% to 3% of B12 absorption from food and increases with supplements [2][3].
The liver plays a central role in B12 recycling. Part of hepatic B12 enters bile and undergoes enterohepatic circulation, where approximately 1.4 micrograms secretes daily into the small intestine [2]. Healthy individuals reabsorb about 0.7 micrograms per day from bile [2]. Like how micronutrients that support testosterone require proper absorption and circulation, B12 depends on this complex system functioning correctly.
B12 binds to transcobalamin II in blood for delivery to tissues once absorbed [1]. Cells with transcobalamin II receptors take up the vitamin and convert synthetic forms like cyanocobalamin into biologically active methylcobalamin and adenosylcobalamin [5]. This multi-step process explains what causes b12 deficiency in older adults: any breakdown in stomach acid production, intrinsic factor secretion, pancreatic enzyme activity or intestinal receptor function disrupts the entire system.
What causes B12 deficiency in older adults
Reduced stomach acid production
Atrophic gastritis stands as the main cause behind vitamin b12 deficiency over 60. This chronic stomach inflammation destroys acid-producing cells in the gastric lining and results in hypochlorhydria or complete achlorhydria [8]. The condition affects older adults disproportionately, with studies documenting its presence in much of the elderly population [8].
Stomach acid serves a critical function beyond digestion. It liberates B12 from the proteins that bind it in food sources like meat and fish. B12 remains trapped and unavailable for absorption without adequate acidity. Type A gastritis involves the fundus and body of the stomach whilst sparing the antrum, whereas Type B gastritis affects all regions [8]. Type A associates with autoimmune processes, whilst Type B links to Helicobacter pylori infection, alcoholism and certain medications [8].
The effect extends beyond simple malabsorption. Chronic atrophic gastritis creates an acid-free stomach environment that alters B12 processing fundamentally [8]. This slow, progressive deterioration can lead to peripheral neuropathy, depression and cognitive decline over time [8].
Medications that interfere with B12 absorption
Proton pump inhibitors alter B12 absorption by reducing gastric acid secretion needed to convert dietary protein-bound B12 to its free form [9]. Research demonstrates that PPI use associates with diminished serum B12 levels, with concomitant oral B12 supplementation slowing but not preventing the decline during prolonged use [8]. H2 receptor antagonists show less effect on B12 status compared to PPIs [8].
Metformin, prescribed commonly for type 2 diabetes, interferes with calcium-dependent absorption of the B12-intrinsic factor complex [8]. The risk intensifies with duration and shows substantially higher deficiency rates after four to five years of continuous use [8]. Studies reveal the mechanism involves disruption of B12 uptake in the ileum and reduces bioavailability [8].
Calcium supplementation emerges as a potential effect modifier. Research suggests calcium supplements might restore B12 absorption in various conditions, though the interaction with gastric acid inhibitors requires careful monitoring [9]. Patients taking multiple medications face compounded risks, especially when you have elderly individuals on both metformin and PPIs at the same time [8].
Dietary factors and vegetarian diets
Vitamin B12 deficiencies occur often if you consume plant-predominant diets, including those who consume dairy and eggs [8]. As opposed to earlier beliefs that deficiency affected strict vegans only, evidence now shows deficiency demonstrates frequently even among lacto-ovo vegetarians [8].
The timeline surprises many. Deficiency can develop within the first two years of starting a plant-predominant diet and contradicts the misconception that it takes many years [8]. Research documents that 53.8% of vegetarians presented with low B12 levels below 203 pg/ml [8]. Males and those not taking B12 supplements showed lower markers of B12 status [8].
The B12 content in eggs and milk remains quite low. Appreciable loss in content or bioavailability occurs when milk undergoes processing and eggs are cooked [8]. Whilst fortified plant-based milk alternatives serve as important B12 sources, most patients consuming plant-predominant diets fail to get adequate amounts through diet alone [8][8].
Pernicious anaemia and autoimmune conditions
Pernicious anaemia represents an autoimmune condition where the immune system produces antibodies attacking cells in the stomach's mucosal lining and nerve cells [8]. These antibodies block intrinsic factor, the critical protein that carries B12 from food to absorption sites in the small intestine [8].
The condition occurs more commonly in women around 60 years of age, people with family history and those with other autoimmune conditions [8]. People over age 60 of Northern European or Scandinavian descent face elevated risk, though it affects people from other ethnic backgrounds [8].
A greater association exists between pernicious anaemia and other autoimmune diseases than predicted, including thyroid disorders, type 1 diabetes mellitus and Addison disease [10][8]. Given that genetic factors influence susceptibility, family history serves as an important risk indicator [8]. The autoimmune destruction of parietal cells proves irreversible and necessitates lifelong supplementation for affected individuals [8].
Symptoms of B12 deficiency in elderly
Symptoms often emerge so gradually that people and their healthcare providers attribute them to normal ageing. This subtle onset creates a diagnostic challenge, especially when neurological signs can appear without any blood abnormalities [8]. The clinical picture varies widely and ranges from barely noticeable changes to severe impairment that affects multiple body systems [10].
Early warning signs
Fatigue ranks as the most common original sign, though its non-specific nature leads to misattribution [11][8]. People may notice persistent tiredness that rest does not relieve, coupled with a general lack of energy that interferes with usual activities [8]. Neurological symptoms can present as the sole indication of deficiency and appear months or even years before any blood count changes develop [11][12].
Peripheral neuropathy announces itself through paraesthesia in the hands and feet [11][8]. These sensations become more persistent than occasional numbness from pressure and are described as pins and needles or tingling [8]. Problems with proprioception and vibration sense develop and affect the legs more than the arms in a symmetrical pattern [8][12]. Balance difficulties emerge at this point and show as unsteadiness while walking or an increased risk of falls [8][10].
Mood disturbances surface early in the deficiency process. Depression, irritability and mild anxiety can develop before other symptoms become apparent [11][8][13]. These psychiatric signs occur even when blood tests show normal haemoglobin levels and mean corpuscular volume [8]. These changes happen without anaemia, so they often escape recognition as B12-related issues.
Memory loss and confusion
Cognitive impairment presents in ways that resemble dementia and creates diagnostic confusion [11][8]. Memory problems, difficulty concentrating and reduced focus affect daily activities [8][8]. People struggle to complete familiar tasks and may appear forgetful in conversations [10]. The mental fog described by patients lifts with treatment and distinguishes it from irreversible cognitive decline [8].
Psychiatric symptoms range from mild neurosis to severe forms [8]. Confusion and altered mental states develop as deficiency worsens [13][8]. Delirium, delusions and paranoia can emerge in severe cases and mimic serious psychiatric disorders [8][8]. These neuropsychiatric features can present as the only symptoms related to deficiency and precede haematological signs by long periods [11][8].
The mechanism involves disrupted methylation processes and homocysteine accumulation, both toxic to neurons [8][12]. S-adenosyl-methionine deficiency affects neurotransmitter synthesis and includes serotonin, norepinephrine and dopamine [12]. Myelin degeneration disrupts nerve signalling and produces symptoms from memory loss to severe motor dysfunction [8].
Physical symptoms beyond the brain
Anaemia develops over many years in some cases, with symptoms not appearing until the condition becomes severe [8]. Shortness of breath and rapid heartbeat occur as the body attempts to compensate for reduced oxygen-carrying capacity [11][13]. The heart beats faster to ensure adequate oxygen reaches organs and tissues [11].
Glossitis, characterised by a smooth, red, sore tongue, affects some people [11][8]. Mouth ulcers may accompany this tongue inflammation [13]. The skin can take on a pale or yellowish appearance as faulty red blood cells break down and release bilirubin [11]. This jaundice-like presentation results from the liver processing damaged cells [11].
Digestive symptoms include nausea, diarrhoea and loss of appetite [11][13]. These gastrointestinal disturbances occur when insufficient oxygen reaches the gut [11]. Weight loss follows decreased appetite over time [8]. Muscle weakness, diminished reflexes and problems with movement coordination develop as peripheral nerve damage progresses [11][12]. Both urinary and faecal incontinence can occur in advanced cases [8].
How symptoms differ from normal ageing
The overlap between vitamin b12 deficiency over 60 symptoms and typical ageing changes explains why deficiencies go unrecognised [10][10]. Weakness, fatigue, balance problems and memory difficulties occur in older adults from various causes [10]. This similarity leads to symptoms being dismissed or misdiagnosed as age-related decline [10].
The combination of cognitive and physical symptoms that occur together provides a major clue to B12 deficiency rather than normal ageing [8]. Gastrointestinal symptoms that start around the same time as memory problems should raise suspicion [8]. The reversibility of symptoms with treatment distinguishes B12 deficiency from irreversible ageing processes, with improvements often noticed within weeks of supplementation [8][10].
B12 and dementia: Understanding the connection
The homocysteine link
Research establishes elevated homocysteine as a vascular risk factor with direct implications for brain health. Plasma homocysteine exceeding 14 μmol per litre increases dementia risk by 90%. Alzheimer's disease risk rises proportionally [10]. Each 5 μmol per litre increment in homocysteine lifts Alzheimer's risk by 40% [10]. The Framingham Study documented nearly doubled dementia rates in people with the highest quartile of plasma homocysteine levels [10].
The connection operates through multiple pathways. Elevated homocysteine causes neurotoxic effects that include oxidative stress and vascular damage [14]. Homocysteic acid, a metabolite of homocysteine, acts as an N-methyl-D-aspartate receptor agonist and triggers excitotoxic damage to neurons [10]. More than that, homocysteine promotes copper-mediated and β-amyloid-peptide-mediated toxic effects in neuronal cell cultures. It also induces apoptosis in hippocampal neurons [10].
B12 deficiency disrupts homocysteine metabolism. B12 functions as a coenzyme that aids the conversion of homocysteine to methionine [15]. Homocysteine accumulates in bodily fluids and tissues without adequate B12 [16]. Patients with Alzheimer's disease show lower B12 levels and higher homocysteine concentrations compared to people without dementia [12].
B12's role in brain cell protection
Vitamin B12 maintains brain structure through several protective mechanisms. The vitamin proves essential to myelin formation and maintenance. It acts as insulation for nerve fibres [15]. Myelin can break down when B12 levels fall. This leads to nerve damage that shows up as cognitive impairment [15]. S-adenosylmethionine synthesis depends on B12 and supports both myelin and neurotransmitter production [15].
B12 supplementation has showed remarkable neuroprotective effects. Studies show that B vitamins virtually halt grey matter atrophy in brain areas related to Alzheimer's disease. They also slow cognitive decline [10]. B12 treatment reduces brain water content and improves motor function recovery in traumatic brain injury cases [14]. The vitamin stabilises microtubules and aids remyelination. It inhibits apoptosis through the endoplasmic reticulum stress pathway [14].
Can B12 deficiency mimic dementia
B12 deficiency produces cognitive impairment that closely resembles dementia presentation. People appear forgetful and confused. They struggle with concentration and task completion [17]. Delusions and paranoia develop in severe cases and mimic advanced dementia [17]. Physicians find no reliable way to distinguish between B12 deficiency and dementia based on cognitive symptoms alone [17].
Low B12 levels occur in 29% to 47% of dementia patients [10]. Mental changes may precede haematological signs by months or years. Sometimes they present as the original or only symptoms [10]. Studies of patients with B12 deficiency after gastric resections found 50% displayed intellectual impairment. Only 14% showed megaloblastic bone marrow changes [10].
Is B12 deficiency memory loss reversible
Treatment outcomes depend heavily on timing. Early identification and replacement therapy cause substantial symptom reversal [12]. Among patients with serum B12 levels above 100 pg/mL, 84% experienced substantial symptomatic improvement. They also showed improvements in cognitive test scores [12]. The effects of supplements become noticeable within weeks [17]. But chronic dementia responds poorly to treatment. Metabolic evidence of B12 deficiency still warrants intervention though [10].
Diagnosing B12 deficiency after 60
Blood tests and what the numbers mean
Testing for vitamin b12 deficiency over 60 presents complexities that standard laboratory values alone cannot resolve. Serum cobalamin levels below 200 nanograms per litre indicate deficiency in most cases [16]. The reference range spans from 180 to 914 ng/L for adults, though interpretation requires clinical context with laboratory results [18]. Clear-cut deficiency shows levels below 145 ng/L, often under 100 ng/L [18].
A borderline range exists between 145 and 180 ng/L. People in this range may have early B12 deficiency or represent healthy low-normal variants [18]. Patients with levels below 100 ng/L demonstrate clinical or metabolic evidence of deficiency [16]. Therapeutic trials become necessary when results fall into grey areas, and clinical response confirms the diagnosis [18].
Why standard B12 tests may miss deficiencies
Standard serum B12 measurements prove unreliable as the sole diagnostic tool. 50% of patients with functional B12 deficiency have serum levels above 200 pg per mL when metabolic markers reveal tissue deficiency [15]. The test misses between 10% and 26% of actual cases when used alone [15].
Total B12 tests measure both active and inactive forms that circulate in blood. These include holotranscobalamin and holohaptocorrin [19]. Cells can use only the active holotranscobalamin form [19]. Serum values then appear normal or even elevated while cells remain deficient [20]. Transport protein dysfunction and nutrient imbalances affecting B12 metabolism cause B12 to accumulate in blood despite cellular starvation [20]. Liver or kidney conditions produce the same effect.
Additional markers: MMA and homocysteine levels
Methylmalonic acid and homocysteine measurements provide superior diagnostic accuracy. A study of 406 patients with confirmed B12 deficiency showed that 98.4% had elevated serum MMA levels and 95.9% had elevated homocysteine [15]. Combined testing achieves 99.8% sensitivity [15]. These metabolic markers rise before haematological changes appear and serve as early indicators of tissue deficiency [15]. MMA proves more specific for B12 deficiency than homocysteine, which also elevates in folate deficiency [15]. Renal disease elevates MMA through decreased urinary excretion and requires cautious interpretation [15].
Treatment and supplementation strategies
Image Source: The Independent
Oral supplements vs injections
Both routes work just as well to normalise serum B12 levels after one to four months [17]. Oral supplementation at 2,000 mcg daily raises blood levels better than intramuscular injections at 1,000 mcg, though 1,000 mcg daily orally matches 1,000 mcg intramuscularly [17]. High-dose oral therapy achieves its effect through passive diffusion and absorbs approximately 1% to 3% even without intrinsic factor [3].
Injections bypass absorption barriers and deliver 100% bioavailability into the bloodstream [21]. Hydroxocobalamin remains in the body longer than cyanocobalamin, which allows maintenance therapy at three-month intervals [22]. Patients with neurological involvement require hydroxocobalamin 1 mg on alternate days until no further improvement occurs [23].
How long does treatment take to work
Neurological symptoms begin to improve within one week. Complete resolution occurs between six weeks and three months [23]. Energy improvements surface within two to four weeks with oral supplementation [24]. B12 replacement corrects macrocytic anaemia within two months when done right [23].
Dosage recommendations for older adults
Adults over 50 should think over 500 mcg supplements to maintain healthy B12 levels [25]. Treatment dosages range from 1,000 to 2,000 mcg daily to correct deficiency [3].
Monitoring your progress
Full blood counts should occur within 7 to 10 days of starting treatment, then after 8 weeks [23]. B12 level monitoring becomes unnecessary once treatment commences [23].
Conclusion
Vitamin B12 deficiency affects much of the population over 60 and often masquerades as normal ageing or dementia. The good news? Early detection and treatment can reverse most symptoms, including memory loss and cognitive decline. Neurological improvements appear within weeks of starting supplementation.
If you're over 60, request B12 testing among metabolic markers like methylmalonic acid and homocysteine to diagnose accurately. Treatment proves effective when started promptly, whether through high-dose oral supplements or injections. Don't dismiss fatigue, memory problems, or balance issues as inevitable risks of ageing. These symptoms deserve investigation, as addressing B12 deficiency can restore cognitive function and quality of life.
Key Takeaways
Understanding B12 deficiency after 60 can help prevent misdiagnosed cognitive decline and restore quality of life through proper treatment.
• B12 deficiency affects 20-40% of adults over 60 due to reduced stomach acid production, medications like PPIs and metformin, and decreased absorption capacity with age.
• Symptoms mimic dementia but are often reversible - memory loss, confusion, fatigue, and balance problems can improve within weeks of proper B12 supplementation.
• Standard B12 blood tests miss up to 26% of deficiencies - request additional testing for methylmalonic acid and homocysteine levels for accurate diagnosis.
• High-dose oral supplements (1,000-2,000 mcg daily) work as effectively as injections for most people, with neurological improvements typically beginning within one week.
• Early detection is crucial for full recovery - chronic deficiency may cause irreversible nerve damage, making prompt treatment essential for optimal outcomes.
The key message: Don't dismiss cognitive symptoms as normal ageing. B12 deficiency is a treatable condition that can dramatically improve brain function and overall health when identified and addressed properly.
FAQs
Q1. At what age does vitamin B12 deficiency become more common? B12 deficiency becomes significantly more prevalent after age 60, affecting approximately 20% of elderly individuals, with rates rising to 40% in some populations. This increase occurs because the body produces less stomach acid with age, which is essential for releasing B12 from food sources. Additionally, the small intestine becomes less efficient at absorbing the vitamin, and certain medications commonly prescribed to older adults can interfere with B12 absorption.
Q2. Can vitamin B12 deficiency cause symptoms that look like dementia? Yes, B12 deficiency can produce cognitive symptoms that closely mimic dementia, including memory loss, confusion, difficulty concentrating, and problems completing familiar tasks. In severe cases, it can even cause delusions and paranoia. The crucial difference is that B12 deficiency-related cognitive decline is often reversible with proper treatment, whereas true dementia is not. This is why testing for B12 deficiency is essential when cognitive symptoms appear.
Q3. How quickly can B12 supplements improve symptoms? Most people notice improvements relatively quickly after starting B12 treatment. Energy levels typically improve within two to four weeks, whilst neurological symptoms like memory problems and confusion often begin improving within one week. Complete resolution of neurological symptoms usually occurs between six weeks and three months. However, the speed of recovery depends on how severe the deficiency was and how long it existed before treatment began.
Q4. Are B12 injections better than oral supplements for treating deficiency? Both oral supplements and injections are equally effective at normalising B12 levels. High-dose oral supplements (1,000-2,000 mcg daily) work just as well as injections for most people because they rely on passive diffusion rather than the body's normal absorption process. Injections may be preferred for individuals with severe absorption problems or those who cannot tolerate oral supplements, but for the majority of people, oral supplementation proves sufficient and more convenient.
Q5. What blood tests are most accurate for diagnosing B12 deficiency? Standard serum B12 tests alone miss up to 26% of actual deficiencies. For accurate diagnosis, request additional testing for methylmalonic acid (MMA) and homocysteine levels alongside the standard B12 test. These metabolic markers are more sensitive indicators of tissue-level B12 deficiency, with combined testing achieving 99.8% sensitivity. MMA is particularly specific for B12 deficiency, whilst homocysteine can also indicate folate deficiency, making the combination of tests more reliable than B12 measurement alone.
References
[1] - https://www.ncbi.nlm.nih.gov/books/NBK559132/
[2] - https://veganhealth.org/vitamin-b12/vitamin-b12-absorption/
[3] - https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
[4] - https://nutritionsource.hsph.harvard.edu/vitamin-b12/
[5] - https://pmc.ncbi.nlm.nih.gov/articles/PMC5130103/
[6] - https://pubmed.ncbi.nlm.nih.gov/35337622/
[7] - https://www.bbc.co.uk/food/articles/vitamin_b12
[8] - https://pmc.ncbi.nlm.nih.gov/articles/PMC3824448/
[9] - https://pmc.ncbi.nlm.nih.gov/articles/PMC12879850/
[10] - https://psychiatryonline.org/doi/full/10.1176/jnp.12.3.389
[11] - https://www.medicalnewstoday.com/articles/324265
[12] - https://pmc.ncbi.nlm.nih.gov/articles/PMC7077099/
[13] - https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/symptoms/
[14] - https://www.sciencedirect.com/science/article/pii/S266645932500040X
[15] - https://www.aafp.org/pubs/afp/issues/2003/0301/p979.html
[16] - https://swlimo.southwestlondon.icb.nhs.uk/clinical-guidance/nutrition-and-blood/vitamin-deficiency/vitamin-b12/
[17] - https://www.aafp.org/pubs/afp/issues/2022/0600/p663.html
[18] - https://www.gloshospitals.nhs.uk/our-services/services-we-offer/pathology/tests-and-investigations/vitamin-b12-and-serum-folate/
[19] - https://www.nice.org.uk/guidance/mib40/resources/active-b12-assay-for-diagnosing-vitamin-b12-deficiency-pdf-63499159342789
[20] - https://www.wholemindhealth.co.uk/articles/why-standard-blood-tests-for-vitamin-b12-can-be-misleading
[21] - https://www.surgo.com/b12-injections-vs-oral-supplements-which-is-right-for-you-vitamin?srsltid=AfmBOoq4QHjzzguIxwIwJ3axeIr6M4SLrvIjUNuobS8RKQUk_U_zY813
[22] - https://nhssomerset.nhs.uk/news/document/b12_-_advice_on_investigation_management/
[23] - https://swlimo.southwestlondon.icb.nhs.uk/wp-content/uploads/2022/12/Investigation-and-management-of-vitamin-B12-deficiency-in-Primary-Care-for-adult-patients-v1.1.pdf
[24] - https://www.boltpharmacy.co.uk/guide/how-long-does-it-take-for-b12-to-work
[25] - https://www.everlywell.com/blog/vitamins-supplements/how-much-vitamin-b12-should-a-person-over-65-take/?srsltid=AfmBOooUcPdXiOM4v17t6NCxzQfdXx6RT-Ur1mcVkc9SayXdiIF7fmZH
