People who have in general a very low blood pressure -and especially when they suffer from -dizziness when getting up in the morning or in general from the sitting position may be lacking vitamin B12. [nobody should jump up from his bed like a lion when waking up……that is not what the Shulchan Aruch is meaning to say]
In case you have these problems you may want to try to suck for a few weeks a tablet of B12 [buy only METHYLcobalmine] 1000 mcg ],and let me know if this was useful.