Welcome @kathl, I noticed that you wished to post a URL to the helpful info from Mayo Clinic Labs with your post. You will be able to add URLs to your posts in a few days. There is a brief period where new members can't post links. We do this to deter spammers and keep the community safe. Clearly the link you wanted to post is not spam. Please allow me to post it for you.

- Vitamin B12 Assay, Serum https://www.mayocliniclabs.com/test-catalog/Overview/9154

Do you have experience with abnormal vitamin B12 levels?