Thiamine Deficiency Symptoms: What to Watch For

ByMorgan Eye

Updated June 17, 2025

What are the real-life symptoms of thiamine deficiency?

We’re not just talking textbook definitions for thiamine deficiency symptoms. When thiamine is lacking in your system, things can go sideways in a bunch of surprising ways—often before bloodwork shows anything dramatic.

Here’s what people commonly experience:

• Low energy or crushing fatigue: Thiamine is crucial for converting carbs into usable energy. Without enough, even simple tasks can leave you drained.
• Brain fog and memory issues: Trouble concentrating? Forgetting things more often? Thiamine helps your brain cells communicate.
• Irritability or mood swings: Feeling snappy, anxious, or unusually emotional could be a signal from your nervous system.
• Pins and needles: Tingling, especially in hands and feet, can point to nerve irritation (a condition called peripheral neuropathy).
• Muscle weakness or aches: You might feel physically wobbly or weak, without a clear reason.
• Heart flutters or palpitations: Severe deficiency can mess with your cardiovascular system.

And in more serious cases, low thiamine can lead to conditions like Wernicke encephalopathy (confusion, loss of coordination, and eye movement problems) or beriberi, a disease that damages your nerves and heart.

Who’s most at risk for thiamine deficiency—and why?

You don’t need to be malnourished to have low thiamine. Here are some surprising (and common) situations that increase risk:

• Chronic stress or high carb diets: Your body burns through thiamine faster when you’re stressed—or eating lots of processed carbs.
• Alcohol use: Alcohol interferes with both absorption and storage of thiamine.
• Digestive issues: Conditions like IBS, Crohn’s, or gastric bypass surgery can reduce absorption.
• Older adults: Thiamine needs go up with age, but absorption can decline.
• Pregnancy and breastfeeding: These life stages increase nutrient demand.
• People with diabetes: Some studies suggest a link between low thiamine levels and insulin resistance.

Even things like frequent diuretic use (for high blood pressure or heart conditions) or diets low in whole grains and animal proteins can chip away at your thiamine reserves over time.

Why is it so easy to miss?

Here’s the kicker: thiamine deficiency symptoms often overlap with other conditions—burnout, depression, anxiety, anemia, even perimenopause. Plus, thiamine isn’t always included in routine blood panels.

That means someone could go months—or years—feeling tired, foggy, or “off” without getting a clear answer. In fact, some researchers argue that mild or borderline thiamine deficiency is significantly underdiagnosed, especially in people who are otherwise well-nourished.

Some clues to watch for:

• Do symptoms get worse after high-carb meals?
• Do you feel better after taking a B-complex vitamin?
• Has your energy dropped off without a clear cause?

Only a healthcare provider can diagnose you properly, but these questions might help guide a conversation.

Still unsure if it’s thiamine—or something else?
Menopause fatigue or
burnout recovery could be worth a look.

Sometimes, it’s not one thing—it’s a tangle of small imbalances. The more you learn, the clearer things get.

How can thiamine levels be restored?

The good news? Once spotted, thiamine deficiency is usually fixable—often quickly.

You might need a high-dose thiamine supplement (especially if you’re significantly depleted), but boosting your intake through food also helps. Look for:

• Whole grains
• Pork
• Legumes (lentils, black beans, peas)
• Nuts and seeds
• Eggs
• Fortified cereals

Cooking methods matter too—thiamine is water-soluble and heat-sensitive, meaning long boiling or reheating can destroy it. Gentle steaming or quick sautéing is better for retention.

If you’re on any medications or have chronic health issues that affect digestion or nutrient absorption, you may need ongoing supplementation. A registered dietitian or doctor can help tailor a plan.

The Takeaway

Thiamine deficiency symptoms don’t always shout—they whisper. And those whispers might sound like things you’ve brushed off: crankiness, brain fog, aching muscles, or random pins and needles.

But once you know what to look for, it’s easier to connect the dots. Especially if you’re dealing with a combination of unexplained fatigue, high stress, or a less-than-diverse diet.

If this article resonates, don’t ignore that little voice saying, hmm, could this be me? It just might be worth checking.