[mrsD]

When was the last time you had a chest Xray?

There could be something going on there. Another member here had SOB and they finally found an infection by an uncommon bacteria in her lungs.

Difficultly breathing can be also a sign of myasthenia gravis.
So getting a doctor's evaluation is important.

Some people have too many red blood cells...polycythemia vera.
B12 in high doses is not recommended for them...but this is rare.

So there are things you should check out with a doctor if you have SOB.

B12 will fix things that need repair due to nerve damage, etc.
But it cannot fix everything.

Originally Posted by CrimeofPassion

I was taking Jarrow 5000mcg Methyl B12 daily, and after about maybe a month of doing so developed shortness of breath (that was occasionally severe) and tachycardia.

I'd like to continue taking B12, though, and I've been told I should try Hydroxocobalamin or Adenosylcobalamin. Would anyone here recommend one form over the other?

I've been suffering from pectoralis/shoulder pain for 1.5 years now that the doctors couldn't seem to diagnose, and I discovered by accident that megadosing on the Jarrow B12 took my pain away COMPLETELY. It's very confusing - I don't know if that means the pain is being CAUSED by a B12 deficiency or what's going on. But because it made me feel basically 100% better, I'm desperate to continue with it! Alas, I have to breathe, and Jarrow's B12 made me feel like I was honestly suffocating at times.