One of the first symptoms that obviously persisted post Covid early 2020 was high BP, and for most of the following 4 years got put on 5 hypertensives (plus one, removed after 3 weeks) yet I still remained breathless with normal daily standing tasks( from brushing teeth to cooking at stove). Standing/walking steadily got more difficult but breathing/cardio tests/scans showed no anomalies. I self diagnosed POTS with my own NASA test at home, gave the results to my GP who needed lots of badgering to get me referred some distance away to a specialist with a tilt table. That showed I had dramatic postural hypotension after 8 mins with BP dropping from hyper say 140/75 at rest to 60/40, which not surprising caused me to pass out. The consultant insisted it was not POTS as although the HR rose to over 120s this was to compensate for the low BP. I couldn’t pick up the low BP at home only the high HR, neither could my local hospital without the sophisticated tilt table equipment. I have been taken off, or had juggled the timings, of a number of the hypertensives…haven’t actually passed out last few months but that might be because I recognise it’s about to happen and sit/ lie down as quickly as possible. My HR is now conspicuously high ( over 100) a lot of of the day… .just sitting using iPad HR just jumped from 84 to 107. I too had seen the research re Thiamine /B1 possibly being low post covid and started the more easily absorbed version Benfotiamine ( at 600 mg per day) 2 weeks ago…weirdly that evening had the first 3 readings in a row where BP ‘normal’ and HR under 100 in 4 years 4 months , but improvement only lasted 2 days. But longer term might make a difference. Unfortunately now involving my GP, as specialists effectively signed me off, the high HR instantly sends warning signs to him that I am over medicated on thyroid hormones ( a 22+ year old chronic problem that I control with private blood tests and prescriptions but Gp has never understood)…so will have to go thru months of adjusting thyroid doses before he will look again at the disabilitating postural hypotension! It is worth looking at other vitamins/ minerals like B12, ferritin, folate, vit D etc as covid, and fighting illness in general, can deplete them… I still have no sense of smell meaning I have little appetite to eat and perhaps don’t consume enough food to top up depleted levels and do a lot of other supplements.