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Pernicious Anaemia Society
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Do you need more B12 when you exercise?

I have had my best two months in the last 15 months and have started to do some exercise. The last few days I have been feeling more generally tired after going for a walk and not recovering by the next day which I had been doing. So I am back to days of doing very little.

Does exercise increase the need for B12. I am taking Solgar sublinguals 2500 mcg each day with 400 mg of folic acid and a B comlex and multi vitamin and mineral supplement.

My best improvment followed my 3 monthly B12 injection 3 weeks ago but I can't get that for another 2 months. Would an increase in B12 be helpful and any others suggestions as I want my life back.

4 Replies

Exercise does decrease B12. One of the most challenging aspects of managing a B12 deficiency seems to be gauging how much activity is ok and what is going to be too much. The tipping point is different for everyone. It sounds like you've overdone it a bit this time around. You may want to keep a log of your activity and energy levels to begin to get a better idea of what level of exercise/activity is reasonable for you.

I know it's frustrating, but respect your body's limits. You don't expect a car to keep running without gasoline, right? Your fatigue is your body's way of reminding you that you can't really expect one 3 monthly injection to allow you to run marathons.

One of the hardest things I had to get my mind around early on was that, even though I felt energetic after an injection, all that energy had to last me until the next injection. So I had to learn to pace myself.


This is an interesting subject as it seems that the treatment for PA is just 3-monthly injections. That might be fine for an older person with a more sedentary lifestyle, but if you are younger and more active, then how are you supposed to survive on the same dose?

I now self inject when I need it, rather than relying on 2-3 monthly injections at the doctor's surgery. It has definitely helped as I don't have the lows that I did before, so I just feel the same all the time. Having said that, I have never had as much energy as people who don't have PA, and fatigue is a normal part of my existence.

But, everyone is different, and hopefully you will find a level of B12 that works for you and makes you feel better again.


Hi carer999 having had P.A. for 45 years I long ago recognised my physical limitations and adjusted my lifestyle accordingly.

However two years ago I was diagnosed with Type 2 diabetes and was told I "had to exercise" which of course was anathema to me. My wife suggested we go out together for a walk round the "estate" but i struggled with that and eventually I bought a mini exercise bike which is electrically "power assisted" that I can pedal away on whilst sitting in my armchair for 20 minutes every day.

I think that like many of us on here you may have either to continue to supplement between injections or as I have done, negotiate with your doctor for more frequent injections.

I wish you well


I've missed my twice weekly exercise class for the past six months, since I've been so ill with PA, and two months ago had to stop walking the dogs as well. That three mile walk was part of my daily routine and sense of well-being, and I've missed it so much. I'm going to be sixty later this year and have always been determined to remain healthy, fit and active. So this enforced lack of exercise due to horrible PA has really got me down.

After my loading doses recently, I've started self-injecting once a week, and will continue to do so until I feel better. My next official injection at surgery is of course in three months' time! This week I've started walking the dogs again (albeit at a slower pace than previously!) and my aim is to get back to my exercise classes too. I'd rather self-inject twice a week than have to give up exercise altogether and get fat, flabby and unfit!

Have you considered self-injecting, carer999? I was very nervous but it's been absolutely fine, and it's great to feel in control of my health again instead of at the mercy of an unsympathetic doctor. It's really not difficult (nor expensive) self-injecting subcutaneously, and I'm soooooo enjoying the feeling of returning energy and joie de vivre, and the lifting of that awful blanket of grey fog.

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