HOW I DO – Anemia – PART – 25
HOW I DO – Anemia – PART – 25
(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)
Question: In last part, we covered some other points re anemia with low MCV 1. MDS i.e. myelodysplastic syndrome, Anemia of Chronic Disease (or anemia associated with Systemic Inflammation), Lead poisoning (most commonly from some Ayurvedic medicines/supplements) are some important causes. 2. Uncommon causes include alcohol use, copper or zinc deficiency, and medicines like Isoniazid, Linezolid.
What about anemia with high MCV?
Answer: Most common cause in our country, region for anemia with high MCV is deficiency of Vitamin B12. When we see an MCV over 120, diagnosis is almost always B12 deficiency. This can then be confirmed by another very important sign on peripheral blood smear i.e. macro ovalocytes. These are large oval shaped red cells. In my early years of practice, when B12 level test was expensive, we used to treat people based on blood smear findings. Coupled with basic history and examination. Common finding on examination for these patients is a mild icterus with a typical yellow color, when present. Nowadays we confirm with B12 level. Anemia associated with B12 deficiency develops slowly, like most nutritional deficiencies. Hence patients are not very symptomatic until a severe drop in Hb level.
Que: Ok. So what you are saying is if MCV is very high, then suspect B12 deficiency as the most likely reason. And can be confirmed by blood smear, and B12 level. But why is B12 deficiency so common nowadays?
Ans: Yes. And in family practice, if history and examination do not suggest another cause, it is ok to treat with B12 replacement without B12 level. and repeat Hb in 2-3 weeks. If there is no response, additional evaluation or referral is then required. As isolated B12 deficiency responds very well to B12 supplements. B12 can be given as sublingual tablets, which leads to direct absorption. And avoids any absorption issues at level of stomach or intestine. If there is any concern with compliance, B12 can be given as injection as well. Either subcutaneous, intramuscular or intravenous. We prefer low dose subcutaneous i.e. 1 ml once a day for 5 days or so. And then once a month or so. Subcutaneous lower dose is less painful compared to intramuscular, and very low risk of abscess formation. Injection site abscess are common issue with gluteal intramuscular injections, possibly due to hygiene at the site. I see that a lot of people give 2 ml IM dose for several days. Common injectable B12 preparations are highly concentrated. Hence higher dose is not required. Overall yearly B12 requirement for adult is less than 1 mg. In case of deficiency, this can be 5-10 mg at most. Compared to this, each ml of common injectable preparations contains about 1 mg.
Of course, Sublingual is our first preference when we are confident about compliance. As this is most convenient for patient.
With regard to why B12 deficiency is now so common, there is no clear answer. It seems to be an issue of several lifestyle changes. Changes in our diet, water etc has possibly led to this. However, even in same house, with same diet and water source, we see some people develop B12 deficiency, while others do not. Studies from India suggest low intake as main cause, but are unable to figure out why vegetarians now have so much B12 deficiency compared to past. They suggest possible low rate of detection in past as one factor. But it is hard to believe since large populations have been vegetarians for hundreds of years. Talk about filtered water (RO water) as a risk factor is based on one small study, cross sectional. So not a proof, but a possible association. No larger, prospective study to confirm this. Another explanation is lower intake of dairy products, fermented foods. Not conclusive however as some studies have contrary results. For non vegetarians, B12 deficiency is rare, as meat is a direct rich source of B12. For them, it generally means a significant absorption issue e.g. pernicious anemia.
Que: Ok. Since non vegetarians have much lower incidence of B12 deficiency, somehow this means that vegetarian food or lifestyle is associated with low B12 intake. So what to advice our patients?
Ans: Good question. Until research has more clear answers, what do I do for myself or my patients? I recommend most importantly, taking a simple multivitamin supplement. Or a high dose sublingual B12 supplement once a week. Daily high dose is potentially harmful and has association with certain diseases. Hence not recommended daily. For the same reason, I advise against many commercial vitamin supplements that contain large doses of vitamins, much higher than RDA (recommended daily allowance). USA guidelines also advise against vitamin supplements for routine use. In USA, many foods are fortified with B12 and other vitamins, hence for them daily vitamins of any kind are not required. However, for us, a small dose supplement is important, as our food is not fortified. One cannot rely on high intake of fruits and vegetables to supply all vitamins, especially B12. Or even regular intake of fermented foods, dairy products, non RO water etc. Hence it is safer to take once a week or so supplement, to avoid severe deficiency. For those with high motivation, once a year blood tests can be done to ensure that supplements are adequate, neither too high nor too low, for most common vitamins, including B12.
July 5th 2026 Dr Chirag A. Shah; M.D. Oncology/Hematology (USA), 9998084001. Diplomate American Board of Oncology and Hematology. Ahmedabad. drchiragashah@gmail.com www.shyamhemoncclinic.com