What Is The Vitamin B12 Dosage For Seniors?

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Growing up, our parents constantly reminded us to eat our fruits and vegetables; these are rich in essential vitamins that we need to grow up healthy. To our surprise, our need for vitamins has grown with us, and as we age, we need them even more while we lose the ability to absorb vitamins from food properly.  

Vitamin deficiencies are a common health problem, especially at a later age. The elderly are more susceptible to vitamin deficiencies due to many factors such as changes to the gastrointestinal tract, diet, and changes in body composition [1].  

What Is The Vitamin B12 Dosage For Seniors? 

Among the vitamin deficiencies seen in seniors, vitamin B12 deficiency is quite common and tends to increase with age [2].  

What is vitamin B12? Should you start screening yourself for vitamin B12 deficiency? What is the right vitamin B12 dosage for seniors? 

What Is Vitamin B12, And Why Is It Important? 

Vitamin B12, also called cobalamin, is a vitamin derived from red meat, eggs, and dairy. Plants do not produce B12; therefore, most plant-based diets often rely on supplements as a source of B12. 

Vitamin B12 is crucial and beneficial due to its involvement in [3]: 

  •   DNA synthesis 
  •  Supporting blood cells
  •  Maintaining the central nervous system  

Vitamin B12 Dosage For Seniors 

In the elderly, deficiency is usually caused by malabsorption of vitamin B12 or undernutrition. Although the Recommended Dietary Intake (RDI) of vitamin B12 does not vary once adulthood is reached, it is recommended for the elderly to increase their consumption of vitamin B12-rich food. 

what is the vitamin b12 dosage for seniors

Currently, the Recommended Dietary Allowances (RDAs) for Vitamin B12 is 2.4mc a day [3]. 

Vitamin B12 Deficiency In Seniors 


  • Drugs that interfere with either the absorption or metabolism of vitamin B12, such as Proton Pump Inhibitors (PPI), metformin, some epileptic medications, etc. Doctors prescribe PPI medications often to seniors as a treatment for gastroesophageal reflux disease. While metformin is used in the treatment of type 2 diabetes [4,5]. 
  • A long-term plant-based diet lacking fortified foods or B12 supplements. Vegetarians and people with low meat intake at a higher risk of developing vitamin B12 deficiency in the long term [6]. 
  • Malabsorption caused by bacterial overgrowth in the small intestine, Crohn’s disease, etc. [7]. 
  • Food bound cobalamin malabsorption which is currently the most cause of vitamin B-12 deficiency [8]. It is caused by chronic gastritis or Helicobacter-Pylori-associated gastritis. 


While there are plenty of studies suggesting that vitamin B12 deficiency increases the risks of many health problems such as cardiovascular diseases and osteoporosis, it often causes pernicious anemia. 

Pernicious anemia, also called vitamin B12 anemia, increases the risk of further health problems such as gastric cancer, type 1 diabetes, and thyroid issues [9]. Symptoms of anemia include: 

  • Pale skin 
  •  Fatigue
  •  Headaches 
  •  Loss of appetite coupled with weight loss 

And since vitamin B12 is also implicated in maintaining the health of the central nervous system, you should look out for other symptoms such as: 

  •  Strange sensations in the legs, hands, or feet such as tingling, numbness, or “pins and needles” 
  •  Difficulty focusing, remembering, and reasoning 
  •  Difficulty walking 
  • Inflamed (red and swollen) tongue 


Your healthcare provider will first examine any clinical manifestations you might have, such as the symptoms we have just mentioned. The conclusive test for vitamin B12 deficiency is the determination of serum cobalamin levels.  

what is the vitamin b12 dosage for seniors

In addition to checking vitamin B12, another vitamin B, called folate, is checked since folate deficiency causes megaloblastic anemia, which is similar to pernicious anemia. 

In case of vitamin B12 deficiency suspicion though the blood tests revealed normal vitamin B12 levels, other tests can be done to measure: 

  • Serum Methylmalonic Acid (SMA) levels: are usually elevated when vitamin B12 is deficient. This test is not conclusive because SMA levels could be increased due to renal failure. 
  • Homocysteine (an amino acid) levels: may be elevated due to either vitamin B12 deficiency or folate deficiency. 

When vitamin B12 deficiency is confirmed, the doctor will often start the patient on treatment. Here is how. 


The primary treatment for vitamin B12 deficiency is intramuscular injections of B12.  

Patients who do not suffer from a severe deficiency may receive oral supplements of vitamin B12, with doses varying from 1,000 to 2,000 mcg once a day. 

 Recent studies suggest oral supplementation as a primary line for treatment instead of intramuscular injections due to its efficacy and convenience.  

While it is easier, less painful, and invasive to take vitamin B12 supplementation orally, patients would have to take an extra pill daily until, whereas intramuscular shots of vitamin B12 are given 2-3 times a week.  

The treatment duration will vary from one patient to another. 

Is Vitamin B12 Deficiency Reversible? 

For most patients, vitamin B12 deficiency is reversible.  

Once corrected, the symptoms would resolve. Hematological abnormalities are usually corrected within eight weeks.  

Neurological symptoms take more time to resolve and could last months. In fact, for some patients where the cause of the deficiency is irreversible, the treatment would be lifelong and neurological symptoms may never resolve.  

Elderly patients presenting both vitamin B12 deficiency and dementia may not benefit from cognitive improvement [10]. 

The sooner vitamin B12 deficiency is diagnosed and treated, the higher the chance of reversing neurological complications. 

Is Vitamin B12 Deficiency Preventable? 

Prevention and screening go hand in hand. 

 Suppose you have been on a plant-based diet for a long time or have taken any of the medications mentioned earlier. In that case, it is a good idea to screen for vitamin B12 deficiency every year or upon the presentation of the abovementioned symptoms.  

And since vitamin B12 is obtained from food, here is a list of food rich in vitamin B12 [3]. 

  • Beef liver: contains 70.7 mcg of vitamin B12 per 3 ounces
  • Clams: contain 17 mcg of vitamin B12 per 3 ounces 
  • Tuna: contains 9.3 mcg of vitamin B12 per 3 ounces 
  • Salmon: contains 2.6 mcg of vitamin B12 per 3 ounces 
  • Egg: 1 whole egg contains 0.5 mcg of vitamin B12 

Additionally, fortified foods and nutritional yeast also contain sufficient amounts of vitamin B12. 

What Is The Vitamin B12 Dosage For Seniors? Summing Up 

As we get older, our ability to absorb vitamins decreases.  

Vitamin B12 is essential for the central nervous system, blood, and DNA synthesis.  

Yearly screening for vitamin B12 deficiency could save a senior patient from suffering irreversible neurological complications.  

The sooner the deficiency is diagnosed and treated, the more likely it is for the patient to return to normal.  

Additionally, no toxicity has been linked to high doses of vitamin B12, which means it is never a bad idea to eat a vitamin B12-rich diet and take supplements if needed [11].  



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