Pernicious Anaemia Society
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I am suffering from terrible shortness of breath. I have taken my loading injections of B12 (the first one I took a month ago now) and still very bad breathlessness.

I have read that shortness of breath is caused by low red blood cells as they help carry oxygen in the blood. However when my red blood cells appear in the normal range on my blood test results then how can this be what's causing it?

Thank you for your help anyone. Much appreciated

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When I was diagnosed with P A , breathlessness was one of the symptoms that I had . It is the size of the red blood cells that cause the problem . B12 is required to bring the cells to maturity . Immature cells are large and soft . Mature ones small and hard which enables them to pass through the minuscule gaps needed. Large cells with their oxygen cannot do this , so breathlessness occurs. This is how I understood the problem . After my B12 position improved so did the breathlessness .I don't know if this has helped you . Maybe there are other reasons than B12 deficiency for breathlessness ?


I'm pretty sure that it's not just anaemia that causes the breathlessness associated with a B12 deficiency.

One of the things that B12 is involved in is the conversion of methylmalonic acid (MMA) into succinic acid (actually, it's their coenzyme-A forms, but that just complicates things).

Succinic acid is part of the citric acid cycle (you may have learned it at school as the Krebs Cycle or the TCA cycle). This is the process whereby the body extracts energy from glucose. If the citric acid cycle is inefficient this can result in a loss of energy when it's needed.

The good news is that this should start improving once your B12 levels improve.


Hello Briskate. I am also suffering from terrible shortness of breath. I have a very low serum ferritin (even though taking iron supplements) but have noticed a slight improvement since being prescribed stronger iron supplements.

Have you had your serum iron and serum ferritin levels tested? Might be worth a shot.

But take care with iron supplementation if you decide to do it yourself: it's very easy to overdose if your iron levels are not low and iron is one of those things that can be very dangerous if levels are too high.

Also very interested in the reply's from Wedgewood and Fbirder. Something else for me to consider if the iron supplements do not do the business!

Hope you find some answers and feel much better soon.


Thank you for all your replies.

My ferritin was 57 (range 30-400) so I am now taking supplements for this to get it higher. Folate was 12.1 (range 4.60-18.70)

Since I started taking the B12 injections one month ago I feel a lot more awake which is great. However the shortness of breath is still constant and it seems like a struggle to do anything.

Just wondering if anyone knows if there is any medication to help with shortness of breath (until it improves by itself hopefully)? Also if I get my GP to test me with the oxygen blood test finger machine will it show up a problem for something like this? (my Full Blood Count is normal).

Thanks a lot


You can buy an oximeter from Amazon (for reading your blood oxygen level) from Amazon for about £10.


Hi my blood count had always been good but yet I had a lot of problems with shortness of breath. I think in some people the problem can be due to lack of oxygen with anaemia but in others it may be neurological- all nerves can be affected including the ones that control the lungs. I start to need to take deeper breaths and feel short of breath when I miss an injection by more than a few days. It is one of the first things I notice. You say you have had loading doses so it may be that another dose is due? Everyone appears to need a different amount- some people (allegedly) can do OK on 3 monthly but they probably never visit a forum like this. I am best at 2-3 weekly, others need much more. Alternatively some people take sublingual sprays or tablets to keep them going between injections. I find these help most with my finger pains. If I miss them fingers become more sensitive within a week.


I've only just finished the loading doses and I've had the breathlessness from the start and still have now, so I don't think it's because I missed an injection unfortunately. I really hope there's still time for it to improve as it hasn't improved yet (a month after starting injections)

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It all takes time and I found some symptoms got worse before better. good luck!


As others have said it isn't clear exactly what causes the breathlessness experienced by people with a B12 absorption problem. There are various possibilities - it could be anaemia leading to their not being enough oxygen in the blood or it could be something to do with the autonomic system - which detects and responds to what is going on in your body without you being aware of it. I find, even now, that if my blood oxygen levels fall below 97 (a long way above where I'd really be having a problem with oxygen) then I feel really awful and start to get really breathless.

Breathlessness is also a symptom of anxiety - so the fact that you are worrying about it could actually be making it worse - at the very least it is likely to mean that you are noticing it more.


Thanks for all your help!

Just wondering I'm having a doctor run some antibody blood tests for various different conditions I might have - is there one for Pernicious Anaemia I can ask to be included? However my red blood cells on my FBC look okay so does this mean the test automatically won't show I have Pernicious Anaemia anyway?


Not all people with PA have large red blood cells, and not all people with large red blood cells have PA, so it's a poor indicator either way.

There are two antibody tests for PA.

Only one is recommended nowadays and that's the test for anti-IF (Intrinsic Factor) antibodies. If this shows positive then it's pretty sure you have PA. The problem is that 50% of people with PA give a negative result, which isn't too bad if your doctor knows that. Unfortunately many (most??) of them seem to think a negative result totally rules out PA.

The one that's no longer recommended (although many GPs, including mine, still use) is the one for anti-GPC (Gastric Parietal Cell) antibodies. This has the disadvantage of false positives - some people without PA still have these antibodies, especially amongst the elderly.

Personally, I'd ask for both - and be prepared to argue if the anti-IF shows negative.


Okay thank you. That's very useful to know.

Might be a stupid question but if you are really high in B12 (for example just finished loading doses) does that affect the result or has it nothing to do with it?


I've lost the thread here :

if you are really high in B12 (for example just finished loading doses) does that affect the result or has it nothing to do with it?

Does being high in B12 affect which result?


Taking a anti-IF (Intrinsic Factor) antibodies or anti-GPC (Gastric Parietal Cell) antibodies test


See my summary document for interference with the anti-IF test (hint - it depends).

Sorry I've no idea about the anti-GPC test as this is no longer recommended. Although I, personally, think it's a useful additional bit of info.


Any help with the above question would be really appreciated. Thank you :)


I wanted to talk about your ferritin result.

My ferritin was 57 (range 30-400) so I am now taking supplements for this to get it higher.

Your ferritin result is about 7% of the way through the reference range which is dreadful!

Take a look at this link - the table at the bottom is particularly important :

Notice that iron deficiency anaemia lowers iron, ferritin, transferrin saturation percentage and MCV. It also raises total iron binding capacity and transferrin.

B12 deficiency anaemia raises iron, ferritin, transferrin saturation percentage and MCV. It also lowers total iron binding capacity and transferrin.

Haemoglobin is lowered in both.

Apart from the haemoglobin everything else I've mentioned is being pushed in opposite directions by the two different conditions. The end result of this might be blood results that look not too bad, even quite good, you're perfectly fine, go away... Doctors never take into account that people might have more than one kind of anaemia.

Have you ever had a full iron panel done? And a full blood count? If you had had both done you might find that you had some odd results - some that fit one kind of anaemia but not the other kind, for example.

Are you taking prescribed iron supplements? Or are you self-treating? Can you tell us what you are taking and what the dosage is?

I had two different types of anaemia - anaemia of chronic disease and iron deficiency anaemia. It was only when I paid for some private blood tests of my own that I found out what was going on. With the limited tests done by my GP I would never have known. It took me nearly two years to raise my iron and ferritin levels up to optimal or very near it. I only got there in the end by going gluten-free. I still have to supplement though, just to keep my levels optimal. I only get breathless now when I let my iron levels slip.

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I'm now having 28 mg of Iron supplements a day. They aren't on prescription just from boots. I've been doing this for just over a month at the same time I started my B12 loading doses.

I've had a full blood count. Not sure I've had a full iron panel though - what's included in this?



An iron panel for me has included the following :

UIBC - Unsaturated Iron Binding Capacity


TIBC – Total Iron Binding Capacity

Transferrin Saturation %


I've got mine done by paying for testing from Spire/Blue Horizon. The testing also included things like a full blood count which can tell you even more about your iron status.

The amount of iron you are taking is a drop in the ocean. When my iron level was in my boots I was supplementing by taking 207mg of elemental iron per day.

If your doctor took your iron issue seriously, and prescribed for you, this is the information he would use to decide dosage :

Notice there is a difference between the weight of an iron supplement and the amount of elemental (pure) iron in that supplement.

All the supplements listed in that link can be bought without prescription, although you will have to get them from a pharmacy. Not all pharmacies agree to sell without prescription (it is up to the pharmacist whether or not they choose to).

I had no problems getting iron supplements from Tesco Pharmacies and Lloyds. The only one that causes problems for most people is Boots.

Ferrous sulphate/sulfate should be avoided. For most people it is just too vicious on the gut and can't be tolerated. It is the cheapest option though, so doctors often prescribe it.

It is supposed to be best to take iron supplements on an empty stomach. If you can do that, then great. I never could, and had to take them with food.

I took ferrous fumarate 210mg, one taken three times a day. (Each pill contained 69mg of elemental iron.)

I took either these :$_35.JPG

or these :

As you can see they come in boxes of 84, which is enough for 3 per day for 28 days. You could print out the pictures and take them with you to a pharmacy. I'm sure there are other brands available, but those I've listed are the ones that were available to me.

One box cost me about £5 or a bit less the last time I bought them.

Iron supplements cause constipation for many people. To mitigate the effects, take each pill with 500 - 1000mcg vitamin C.

Start with one iron pill a day and go up in dose every few days to a maximum of three.

If you do start taking the iron pills I've suggested then you must get tested regularly. If you absorb iron well you could substantially improve your levels within 3 or 4 months. I didn't absorb it well, and took nearly two years to raise my levels. I tested regularly, and only got levels up to optimal by eventually going gluten-free. The reason for regular testing is that too much iron is poisonous, and you don't want levels to go above mid-range.

If you can't tolerate the iron pills I suggest (iron causes problems for lots of people), don't give up. There are lots of other kinds of iron supplement you can try. Iron bisglycinate (also called Gentle Iron) is popular. It has much less iron in it than ferrous fumarate though.

Since fixing my iron levels I rarely have breathlessness any more. My levels do drop fairly quickly if I stop supplementing, but at the moment I'm only taking one pill three times a week. This is maintaining my levels where I want them, but I will keep checking. I have no other choice.

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Thanks for all your help. Much appreciated :)


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