I have added comments to other posts but not written specifically on the subject of taking B1 sublingually, so, as I had received questions on the subject, I thought I would write a post.
In 2017 when I first read about Dr C it was in connection with treating Parkinson with injections of B1. Injections weren't an option for me, so taking B1 sublingually, so that it enters the bloodstream rather than going through the digestion, seemed the next best thing. I began with one 100mg tablet placed under the tongue each morning, leaving it to dissolve there while I took my shower. After four or five months my friends, independent of each other, remarked that my smile was now reaching my eyes! A sign of the reduction in rigidity. I also had so much more energy that I had enrolled in a couple of classes, painting and Italian. My sense of smell also had returned. At the beginning of 2019, I reduced my intake by missing some days a week. Currently I take a 100mg tablet on Saturday, Sunday, Tuesday, Thursday, - four days out of seven, a dose which suits me now. If I take too much I become hyper, if not enough I am tired. As far as I am aware, Dr C did not comment on sublingual, either for or against. I did write to him to ask his opinion but that was the day he had his stroke so I had no reply.
The sublingual B1 is not HCL, but it doesn't need to be. I believe the HCL version is needed to help the vitamin through the gut, and the sublingual b1 goes straight into the bloodstream not through the gut. You will also notice that not so much is required because when you swallow a capsule or tablet so much gets lost in digestion. I wouldn't like to hazard a guess at how much the equivalent dose between swallow version and sublingual would be, but would suggest that one 100 mg sublingual tablet a day would be a good place to start. If you did decide to increase, do not take more than one tablet at one time as the bloodstream can only absorb so much at one time, I would space them through the day. I have a friend who started on sublingual B1 at the same time as me and had considerably more symptoms, yet one 100 mg tablets helped him as well. It may be that the sublingual version is much more of a one size fits all than the swallow version.
The sublingual B1 comes from 'superior source' and is available from amazon.com, healthmonthly.co.uk, or evitamins.com. They are very inexpensive!
All I can say about them is that they worked for me and if anyone is finding it difficult to find their correct dose in swallow form, they might be worth a try. In fact they have more than "worked for me", they have been a game changer. It is 10 years since my diagnosis. I have lost all rigidity, regained totally my sense of smell, and am full of energy. Currently my only symptom is a slight tremor easily managed by the 200 mg of L-dopa I take a day. I have also noticed that I am still getting better. I keep a check that my dose is right and I'm quite prepared to alter it again if and when necessary.
I hope this helps someone!