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I just learned that this week is low B12 awareness week, so I wanted to talk to you a bit about low B12, what it is, what it does, and what you may be able to do to manage it!

I do have personal experience with this, as it looks likely that my partner Al’s osteoporosis was caused by low B12!  In 2017, he slipped and suffered an acetabular fracture(broke his hip joint), which we eventually discovered was due to osteoporosis- which is likely to be the result of long-term low B12.  His low B12 is due autoimmune pernicious anemia.  So, what is B12, where does it come from, and why does not having enough in your system wreak havoc?

What is B12 and what does it do?

B-12 is one of the B-vitamins.

B12 is a vital part of many systems in your body.

It is part of the sheathes on all of our nerve endings(which is why nerve damage is a common concern).

It also works with B6 and B9(folic acid) to help maintain your memory by managing homocysteine levels in your body(why memory is often an issue).

It is a key element in many cycles your body regularly goes through, and a lack of B-12 can impair a lot of functions.

Where do I find B12?

cheeseburgers on a grill
Many common meals contain plenty of B12!

If you eat a non-vegetarian diet, you are unlikely to have problems getting enough B12 into your body.

B12 is found in meats(chicken, beef, liver, or fish), in eggs and dairy products(like cheese, yogurt, and milk), and in foods that are fortified with B-12(certain soy products, some vegetarian burgers, many bread products, and some cereals).

People who are on a vegetarian or vegan diet without taking B12 supplements are probably one of the larger risk-groups for not taking in enough B12.  If you think you might not have enough B12 in your diet, please try the suggested foods!  Supplements are easily available, either as an individual pill, or as one of the available supplements in a B-complex pill, and can be found in some multivitamins.

Malabsorption is usually the cause

The more common problem is that for some reason even though there is enough B12 in your diet, your body isn’t absorbing it properly.

People who have had portions of their stomach or intestines removed(such as gastric bypass surgery) are the higher risk category for low B12 for that reason.

There are also conditions that interfere with B12 issues, such as Celiac disease and Crohn’s disease.

Tapeworms or certain types of bacteria also can absorb a large percentage of the B12 in your digestive system, preventing it from getting into your bloodstream despite ingesting plenty of it!

Pernicious Anemia

Pernicious Anemia is the condition most commonly associated with low B12.  If you aren’t absorbing B12 and the conditions listed above don’t apply, you are identified as having Pernicious Anemia.

When you reach a certain age, the medical community doesn’t search for a deeper explanation of some conditions.

You want to make sure that you know the actual cause of your condition, and pernicious anemia is one of those descriptive diagnoses that frustrate me.  Like osteoporosis describes the state of your bones(brittle and weak), pernicious anemia is simply the description of your body’s B12 status(you don’t have much).  Knowing why that is happening can be helpful in ensuring you are doing all you can do to correct the problem.

There’s a percentage of the population where the cause is so common that nobody bothers to dig in deeper(older people often have low levels of acid in their stomachs, which affects the absorption process, so if you’re over 60, there’s your cause), but when you’re an outlier like my partner Al is(way too young to have it be an age-related concern), the doctors need to look deeper to find the underlying cause.    Autoimmune pernicious anemia is Al’s diagnosis at this point.

With autoimmune pernicious anemia, your immune system prevents you from getting the B12 you need by destroying all or most of the Intrinsic Factor in your stomach lining.

The intrinsic factor’s job is to connect to the B12 molecules and signal your body to let them pas into your bloodstream – without the intrinsic factor, the B12 doesn’t get absorbed by your body and just passes through your system, unabsorbed.

It looks like Al has possibly had this condition for years with us being totally unaware.  Autoimmune pernicious anemia most frequently occurs during a person’s thirties. There are occasionally children born with pernicious anemia or low B12, which can have severe effects on their development.  Some of those cases appear to be genetic, while others occur when the mother is on a low-B12 diet(vegetarian without supplements).

What happened to Al?

It looks like he has had autoimmune pernicious anemia for a while, and until treatment for this started, he wasn’t getting any B12 in his system, despite eating plenty of it. We can and do store years worth of B12 in our bodies when we have excess, so he probably has actually had the condition for at least several years.

The second endocrinologist Al saw was confused by so many tests coming up in the normal range while Al obviously had something going wrong.  She tested his B12 levels and hit paydirt.  Previous readings, his B12 level had been a little low, but close enough to normal range that nobody got too concerned. Others missed that the measurements were trending downwards(each time he had less B12)

This time, however, his B12 levels were so low that they couldn’t be measured!  She excitedly suggested to us that Al had malnutrition caused by pernicious anemia and sent him to a hematologist to confirm the diagnosis.

One of the side effects of low B12 is that our bodies contain too much methylmalonic acid.  Apparently high levels of methylmalonic acid increase the rate at which our bodies develop osteoclasts, which breaks down bones.  Without a corresponding rise in bone production, bone density can go down dramatically.

This is what weakened Al’s bones so dramatically, causing the osteoporosis!

It took a very long time to get to the bottom of his case(well, we think and hope we’ve reached the bottom) since this is so unusual.  Multiple doctors suggested that he had celiac disease, but the testing they did for it was inconclusive and presumed negative(apparently celiac is one of those conditions where the testing isn’t always accurate).

The hematologist sent Al to get an endoscopy(the hematologist was the second doctor to suggest celiac and find his tests inconclusive).  The endoscopy indicated autoimmune pernicious anemia(atrophic gastritis)and no indication of celiac disease!  We finally had a cause!

Al’s endocrinologist has never had a patient like Al before and is very excited about the whole thing.  Al is getting monthly B12 shots(which he’ll have for the rest of his life) , and we are waiting to see how much his bone mineral density improves.  If we have gotten to the bottom of his health issues, he should have a significant(measurable) increase in his bone mass by next year!

Usual symptoms of low B-12/Pernicious Anemia

woman thinking about B12There are symptoms of low B12, and they can be debilitating or at least extremely uncomfortable – ranging from slight jaundice(yellowing skin) to nerve damage, to dizziness and confusion, or severe fatigue.

It does appear, though, that folic acid tends to mask low B12 symptoms a bit, so even if you don’t have the standard symptoms, you still might have low B12.

It’s also easy to miss B12 deficiency if you have other conditions that cause many of those symptoms.

In Al’s case, he had experienced a brain injury in 2012, which sometimes gave him trouble with his memory or focus, as well as leaving him with a constant headache(which also will affect your ability to focus).

When he broke his hip, his memory did get a bit worse, but we assumed it was the extra stress exacerbating the brain injury damage or the increased pain he was in from the hip damage affecting his focus, not that he had a different condition!

General treatment:

If you have pernicious anemia, your treatment most likely is regular B12 shots.  The exact amount a person gets may vary, but the idea is that if your diet should give your enough B12, but you aren’t showing it, then injecting the B12 into your bloodstream should fix the problem.

Oral vitamins are more helpful if you have low B-12 due to diet – if you can’t absorb much, the vitamins won’t be much help.

If you have confirmed autoimmune pernicious anemia this the only treatment(and the only necessary one), but it is for life.

If you have another cause, it’s possible that treatment of the related condition may improve your B12 levels.  If your diet has been low on B12 sources, a dietary adjustment may be all you need!

You also can take supplements, which may help if you haven’t been getting enough B12 into your body – however since in most forms, it still needs to be absorbed in your stomach and small intestine, B12 absorption issues aren’t improved by taking the supplement orally.

There is some evidence that the sublingual(placed under the tongue to dissolve) B12 may partially go directly into the bloodstream, so it may be worth a try to purchase it in that form, and you may get some benefit while pushing for your shots.  The shots are the most effective treatment for B12 absorption issues.

How do I get mine tested?

Testing for low B12 is as simple as a blood test.  If you are in the risk groups or are experiencing symptoms associated with low B12, you may want to ask your doctor to run the blood test for B12 on you so you can see where you stand.  B12 is not part of the standard blood panel, so you do need to request it.  It does appear that different labs interpret the information slightly differently and have somewhat different values considered ‘low’ and ‘normal’ so unless your B12 is considered high, you may want to do more research if you have symptoms.

If your results come back low or abnormally low, make sure that you are eating enough sources of B12.  If you aren’t, adjust your diet, but if you are, especially if you are also experiencing symptoms of low B12, you may have found your problem.

B12 shots used to be given very often by doctors, but it is no longer common practice.  There are a lot of people with low B12 struggling to get their shots as regularly and as high dosage as they need, but if you lack the intrinsic factor that really is the only viable treatment. As mentioned previously, a lack of intrinsic factor means that no matter how much B12 you ingest, your body won’t be able to absorb it.


Low B12 is a somewhat common condition and is often referred to as pernicious anemia.  Being told you have pernicious anemia is likely not enough to get properly treated or your condition properly managed.  Instead, you want to dig in a bit and learn what form of pernicious anemia you have and/or what caused it in your case.

If you are a strict vegetarian or vegan or otherwise have a very limited diet, it’s possible that you simply aren’t ingesting enough B12, so adjusting your diet and possibly taking B12 supplements is likely the best idea.

If the problem isn’t dietary, there’s likely something going wrong in your digestive tract, and that needs to be identified and either managed(remove or treat the cause) or worked around(regular B12 injections)

An endoscopy might be required to confirm the cause – that is an appropriate next step.  Treating yourself with sublingual B-12 may be a help even if you lack intrinsic factor, but taking B12 supplements will affect your test results so make sure your doctor knows what you are taking and how much.

If you are dealing with a mystery illness, checking your B12 levels may help you get a better picture of what’s going on inside your body

My suggestion is that if you aren’t sure about your B12 levels, and have felt fatigued, dizzy, or forgetful lately(or have osteoporosis of unknown origin!) – you may want to get your B12 levels tested to help you and your doctor(s) get a clearer picture of what’s happening in your body!



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  1. Terrific resource article, Alison. I didn’t know there was an awareness week for B12, but every time I come to your site, I learn something new. This is one supplement that I’ve been really diligent about for years because I don’t eat a lot of meat. My diet is mostly raw. I take a supplement that is a mitochondrial booster for MECFS that is loaded with B12 and a few other goodies and it helps a lot. I notice if I forget a few days.

    1. Yeah, I hadn’t known about B12 awareness week either until I found the information on a pernicious anemia group on fb.
      Given Al’s experience, I thought it was important to share!
      A mostly raw diet? Guess that minimizes your cooking time then!
      So glad you are getting the vitamins you need…it’s so important!

  2. An informative post! I was having nerve/small fibre neuropathy type pain once and tried some B vitamins but unfortunately, strangely, made it worse so I stopped. Do work with doctors and take it slow as it’s a fat based vitamin, too!

    1. Sheryl,
      Thanks for adding that!
      Were you able to find the cause of that neuropathy pain?
      It absolutely is important to work with doctors on this – we wouldn’t have known about his B12 issues without testing as he fitted none of the standard criteria for low B12 to be an issue!

      For Al, it’s all about getting those shots and taking the sublinguals. It’s really disconcerting to see how much the lack of a single vitamin can mass you up!

  3. I’m glad I read this – I’ve been meaning to get this checked up and because of dietary restrictions I’m almost certain I’m not getting enough B12 so thank you for writing about this.

    Sometimes, I feel there are so many things to look at and manage with the body that it can be easy for a Vitamin like B12 to be lost in it all and then be ignored. Thank you once again Alison.

    1. Shruti,
      So glad that you’re finding it helpful! What we’ve learned with B12 is pretty fascinating – it can stay in your system for years, but not having it can be devastating for some systems. I really hope your B12 levels are okay, but the good news is that if they aren’t it’s a relatively easy and inexpensive fix. If dietary restrictions are behind it, most any supplement with B12 will do. If you’re worried about your intestinal track absorbing it, it sounds like sublingual medication is the way to go, unless you just need the shots. I feel fortunate that my levels are okay.

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