| Regarding side effects, I found this at Mayoclinic.com, which is a website of a mainstream highly respected hospital.
"Side Effects and Warnings:
Thiamin is generally considered safe and relatively nontoxic, even at high doses. No clear tolerable upper level (UL) of intake has been established. Doses up to 200mg daily for long-term periods or single doses of up to 8 grams [!]* have been reported as being nontoxic. Dermatitis or more serious hypersensitivity reactions occur rarely.
Large doses, greater than 100mg, may cause drowsiness or muscle relaxation. "
That is a good site for further, conservative info on B-1.
As I mentioned on another thread just yesterday, the B-1 I purchase comes in 100mg tablets, which supply 6667% RDA. That is HALF the long term daily dose Mayo Clinic mentions above. (I usually take 1/4 tablet (25 mg), sometimes a second 1/4 later in the evening.) My gosh that 8 gram single dose they mention is unbelievable, isn't it!? That would be 80X6667=533,360% RDA !
Sorry, I've never looked into the fat soluble source .
* Exclamation point my own.  | 
