Will 100mg Oral Thiamine Affect Your Sleep?
No, taking 100mg of thiamine orally will not keep you up or interfere with your sleep. Thiamine is a water-soluble B vitamin that does not have stimulant properties or known effects on sleep architecture 1, 2.
Why Thiamine Won't Disrupt Sleep
Thiamine has no stimulant mechanism: Unlike caffeine or other stimulants, thiamine functions purely as a metabolic cofactor for glucose metabolism and does not affect neurotransmitter systems involved in wakefulness or arousal 1.
Excess is simply excreted: When body tissues are saturated with thiamine, any excess is excreted in the urine as pyrimidine, and as intake increases further, it appears unchanged in the urine—meaning your body eliminates what it doesn't need without causing physiological effects 2.
No toxicity or side effects at this dose: Parenteral doses of 100-500mg have been administered without toxic effects, and the FDA notes that dosages exceeding 30mg three times daily (90mg total) are simply not utilized effectively by the body 2.
Why You Actually Need Thiamine Supplementation with SIBO
Given your history of SIBO and malabsorption, 100mg oral thiamine is not only safe but potentially inadequate for your needs.
Critical Risk Factors in Your Case
SIBO directly impairs thiamine absorption: Bacterial overgrowth in the small intestine interferes with thiamine absorption through multiple mechanisms, including bacterial consumption of thiamine and bile salt deconjugation that prevents adequate nutrient absorption 3, 4.
Thiamine stores deplete rapidly: Thiamine has the smallest body stores of all B vitamins and can be completely depleted within just 20 days of inadequate intake—far faster than other micronutrients 1.
Malabsorption makes oral supplementation unreliable: Even with oral multivitamin preparations, patients with malabsorption may not absorb thiamine adequately, as demonstrated in cases where patients on oral supplements still developed Wernicke encephalopathy 5.
Warning Signs to Watch For
Seek immediate medical attention if you develop any of these symptoms, as they indicate severe thiamine deficiency requiring IV treatment:
- Mental status changes: apathy, decreased short-term memory, confusion, irritability 3
- Neurological symptoms: peripheral neuropathy with numbness/tingling, disrupted coordination, vision changes (diplopia, ophthalmoplegia) 3, 5
- Cardiovascular symptoms: unexplained hypotension, heart failure symptoms 3, 5
- Persistent vomiting that is debilitating 3
- Unexplained lactic acidosis 3
Practical Recommendations for Your Situation
Oral Dosing May Be Insufficient
100mg oral daily is a reasonable maintenance dose for someone with normal absorption, but with SIBO and malabsorption, you may need higher doses or IV supplementation 1.
Consider 200-300mg oral daily if you have ongoing SIBO symptoms, as this is the recommended dose for patients with malabsorption or chronic conditions affecting absorption 1.
Address the Underlying SIBO
Treating SIBO is essential before supplementation will be fully effective: The British Society of Gastroenterology recommends rifaximin 550mg twice daily for 1-2 weeks, which achieves symptom resolution in 60-80% of patients with proven SIBO 6.
Alternative antibiotics include doxycycline, ciprofloxacin, or amoxicillin-clavulanic acid if rifaximin is not available or effective 6.
When to Consider IV Thiamine
You should receive IV thiamine (200-300mg daily) if you have:
- Persistent vomiting or severe dysphagia preventing oral intake 1
- Rapid weight loss combined with decreased food consumption 3
- Any neurological symptoms suggesting deficiency 1, 3
- Failure to respond to oral supplementation 1
Bottom Line
Take your 100mg thiamine without worry about sleep disruption—it won't keep you up. However, given your SIBO and malabsorption history, monitor yourself closely for signs of deficiency and consider discussing higher oral doses (200-300mg daily) or IV supplementation with your physician if you have ongoing symptoms or poor oral intake 1, 3.