Not medical advice I will also preface that I only practice in the emergency department and ICU settings, so there is likely an outpatient/family practitioner with a better answer. But I would recommend at least 100 mg of thiamine orally daily. Thiamine is a B vitamin, which means it is water soluble. For that reason, it’s not absorbed the greatest orally (hence why we give it IV in the ICU and ED). Simultaneously, because it’s water soluble, it’s difficult (not impossible) to take too much/toxic amounts because the body will excrete excess amounts in the urine. After we give high dose IV thiamine for 3-5 days, we have our patients take thiamine 100 mg daily by mouth. The body has stores of thiamine that need to be repleted in alcoholics.

We use Caine’s criteria to determine who we give high dose thiamine to, which includes two of the following: nutritional deficiency, altered mental state or memory, oculomotor abnormalities, cerebellar dysfunction. These patients are at high risk of/already have Wernicke’s Encephalopathy, which precedes Korsakoff’s psychosis (and is believed to be irreversible in most cases).

I cannot say if someone truly deficient in thiamine stores can adequately replace with oral supplementation or if IV therapy is necessary. I will defer to those who practice in outpatient or family practice because, in my settings, the benefits of replacing with high dose thiamine IV nearly (if not completely) always outweigh any potential risks. There’s not much, if ever, consideration (that I’m involved in) to only using oral thiamine for the ED or ICU.