If you're dealing with ongoing fatigue, heart palpitations, numbness or tingling, or memory issues, thiamine deficiency might be on your differential — even if you'd never think of it. Most people assume thiamine (vitamin B1) deficiency is a third-world problem, but it shows up in modern diets more than people realize, especially in diabetics, in heavy carb consumers, and in anyone with chronic alcohol intake. In this post we'll walk through how thiamine deficiency presents, the systems it affects most, and the situations where it's most likely to develop.
Thiamine works as a cofactor for enzymes that break down carbohydrates — and to a lesser extent amino acids and fatty acids — into usable energy. The most important of those enzymes is pyruvate dehydrogenase, which sits at a critical step in glucose metabolism. Without thiamine, that enzyme doesn't work efficiently. Glucose can't be properly broken down. Instead, the body shuttles excess glucose into making triglycerides, which then get stored as fat.
This is why people who eat a lot of carbohydrates have a higher thiamine requirement. The more glucose coming in, the more thiamine you need to process it. Diabetics, in particular, often run low on thiamine — high blood glucose plus impaired metabolism means thiamine demand outstrips supply over time. (If a diabetic reduces glucose intake, thiamine demand drops too.)
Day-to-day, mildly reduced thiamine intake won't be noticeable. But over the long term, the systems that depend most on cell turnover and constant energy production start to suffer. The result is a symptom cluster that's frustrating to diagnose because it overlaps with so many other things.
Energy and brain function take an early hit. Fatigue and weakness are common. As the deficiency progresses, cognitive symptoms start showing up — confusion, memory impairment, irritability, emotional instability. The mechanism: the nervous system needs huge amounts of ATP to send signals back and forth between neurons. When thiamine is short, ATP production falters. Nerve signals weaken. Neurotransmitter production drops. Eventually neurons themselves can deteriorate.
The peripheral nervous system is particularly susceptible. Numbness and tingling in extremities, difficulty walking, sometimes muscle weakness — these are classic neurological signs of thiamine deficiency. They develop gradually, which is why patients often attribute them to age, posture, or other causes.
The cardiovascular system also depends on thiamine for ATP production — the heart muscle needs energy for every contraction, and the electrical conducting system needs energy for every signal. When thiamine is low:
If you're seeing unexplained palpitations or new arrhythmias and your standard workup is normal, thiamine deficiency is one of the things worth ruling out — particularly if you also fit one of the high-risk categories below.
Loss of appetite, nausea, vomiting, abdominal pain — thiamine deficiency affects the contractility and motility of the digestive tract. This becomes a tricky diagnostic loop: the GI symptoms can drive someone to restrict their diet, the restriction worsens the thiamine deficiency, and the deficiency keeps the GI symptoms going. Patients sometimes go in circles for years on this without catching the actual cause.
In really advanced thiamine deficiency, you can see beriberi. Two main types:
Cases this severe are uncommon today in developed countries. But there's a more dangerous picture related to alcohol: Wernicke's encephalopathy, which can occur in chronic alcohol use. Wernicke's presents with confusion, ataxia (inability to coordinate movements), eye movement abnormalities, and in severe cases coma. Korsakoff's syndrome — a related, more chronic form — adds memory disturbances. These are medical emergencies and are the reason thiamine is given empirically to anyone admitted with alcohol withdrawal or unexplained altered mental status.
The classic high-risk groups in modern populations:
Modern dietary trends — gluten-free, keto, carnivore, plant-based without supplementation — can move people out of fortified grain consumption and into low-thiamine territory. This is often missed because the assumption is "fortified food, you're fine." Once someone leaves that food group, they're not.
The diagnosis can be made by blood test (whole blood thiamine, or transketolase activity is more sensitive). But thiamine is also generally low-risk to supplement, so empirical replacement is reasonable in someone whose symptoms fit. A few practical points:
Thiamine deficiency isn't just a historical or third-world problem — it shows up in modern populations more than most people realize. Diabetics, heavy carb consumers, chronic alcohol users, and people on restricted diets that exclude fortified grains are all at elevated risk. The symptoms cluster around fatigue, neurological complaints (numbness, tingling, memory issues), cardiovascular changes (palpitations, weak contractility), and GI dysfunction — and they're easy to attribute to other causes. If your symptoms fit and you're in one of these risk categories, it's worth investigating.
If you'd like help interpreting your specific situation — whether thiamine fits, what to test, and how to address it — work with me directly. Telehealth appointments available for most US states.
Topics: Thiamine, B1, Vitamin B1, Beriberi, Fatigue, Diabetes, Alcohol, Wernicke's Encephalopathy