Low CO2 level --- has anyone noticed this on thei... - PMRGCAuk

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Low CO2 level --- has anyone noticed this on their lab results?


Just stopping in briefly to ask a question. I hope everyone is doing well.

I'm back to club zero after being diagnosed with PMR about 12 years ago. Prednisone was my best friend for a long time but not so much during the last 3-4 years.

I'm still learning things and this has piqued my interest. I'm reasonably knowledgeable about metabolic lab panels and my blood CO2 level has been low for a long time. I never thought too much about it. My GP brought it up once but as I recall, it didn't seem significant. I personally, felt it was better that it was too low as compared to being too high. I googled it today just to see what might explain it. I found the following:


The part that was most interesting was the following:

Too little CO2 in the blood may indicate: Addison's disease, another disorder of the adrenal glands. In Addison's disease, the glands don't produce enough of certain types of hormones, including cortisol. The condition can cause a variety of symptoms, including weakness, dizziness, weight loss, and dehydration.

I do have a low cortisol level but according to my endocrinologist it is adequate. I never had a synacthen test because my endocrinologist says that my adrenals haven't had time to recover.

Any comments would be appreciated. ... thanks

10 Replies


All I can add is that the Synacthen Test measures potential rather than actual Cortisol production.

Hidden in reply to SheffieldJane

Hello! ... sorry to hear about the setback. I'm recovering from 60 mg at this time last year and I hope and pray that it won't happen again.

Have you considered your breathing? I have taken Buteyko breathing lessons and a big thing taught is over breathing which lowers Co2 blood levels. This could be from mouth breathing for one thing. Some info here. I have no affiliation but it might be of some use to you.


Hidden in reply to rick518

That is a good point. Funny that I was in a position where I needed to always consider how other people were breathing but never gave my own breathing much thought. I do have breathing issues but they are the kind where I would expect my Co2 level to be high. Mine are consistently low.

Thank-you for the link. "Disproportionate breathlessness" is terminology that I have never used and seems to express it well. It seems to be frequent complaint on this forum so it is beginning to get interesting.

rick518 in reply to Hidden

It is worth looking into then because the more we deep breath the more C02 is exhaled

The Synacthen test is to show whether the adrenal glands are capable of working if given an artificial hormone that simulates stimulation from the pituitary. Therefore, it would tell you if your glands are capable of working, not if they are working. Knowing they are capable is very useful and it may be they indeed just need time or the problem may be at the pituitary end not with the glands.The first Synacthen test would also provide a baseline to see if there has been any improvement. I had one done at 4mg and another done at 0.5mg which showed a big step up from adequate. They also did a Cortisol blood level which was ok ish to start but they wanted good so it was repeated 6 months later. Even with that, they want to check in a year to make sure continued function. Sounds like your Endo is happy for your engine to run on 3 cylinders rather than 4.

Hidden in reply to SnazzyD

My endo is happy that my adrenal engine is running on 2-3 cylinders and not 0-1 cylinders. She thinks getting to 4 will take a long time. She will consider a synacthen test if my engine gets me down the road and doesn't stall out for 6 months. She is following along and wants to know if I need any hydrocortisone. For now, and has given me a good supply of hydrocortisone just in case.



The main point seems to be that in itself it isn't seen as too much of a problem - it will be the underlying cause that could cause concern. But presumably your doctor doesn't see anything that worries them?

When I had adrenal problems and asked my endocrinologist whether I had Addisons he pointed out that Addisons is something you are generally born with or caused by a tumour. What we have, having been on Pred long term, is like 'a medically induced form of Addisons' but not Addisons itself, if that makes sense.

Hidden in reply to tangocharlie

It makes perfect sense. You are absolutely correct. "Secondary adrenal insufficiency" caused by chronic pred use can be just as serious as Addison's.

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