B1 Deficiency: Symptoms of thiamine (B1 deficiency)

Below are some of the most common symptoms of Vitamin B1 deficiency.

Thiamine (vitamin B1) is an important nutrient for taking energy from food and turning it into energy for your brain, nerves and heart. It is needed by the body to process carbohydrates, fats, and proteins – but it is most important for how we process carbohydrates (sugars and starches).

1. Loss of appetite

Experiencing an atypical loss of appetite can be one of the earliest symptoms of thiamine deficiency. Losing your appetite (not feeling hungry) can lead to unintentional weight loss, which can be problematic or unsafe.

2. Fatigue

Being deficient in thiamine can show up as fatigue (tiredness), which may come on quickly or over time, depending on the severity of the deficiency. If you suspect poor sleep may be the cause of your fatigue, click here for our comprehensive sleep guide

3. Irritability

Having a thiamine deficiency may cause some changes in your mood, such as making you more irritable or easily upset.

4. Nerve damage

Among the most well-known side effects of prolonged, severe thiamine deficiency (beriberi) is damage to the nerves, also known as neuropathy.

Potential symptoms of beriberi can include

• tingling limbs
• loss of sensitivity in feet and fingers
• muscle weakness
• rapid heartbeat
• difficulty waking up
• mental confusion
• coordination problems

5. Tingling arms and legs

Even though tingling — the sensation of prickliness and “pins and needles” in your arms and legs, also called paraesthesia — can be a symptom of severe beriberi, it can also be an earlier symptom of thiamine deficiency.

6. Blurry vision

Because of the role thiamine plays in maintaining healthy nerves, a deficiency can affect the optic nerve in your eyes.

Specifically, this can cause swelling of the optic nerve that leads to blurred vision. Left untreated, optic nerve damage can eventually result in vision loss.

7. Nausea and vomiting

Like fatigue and irritability, nausea and vomiting can be nonspecific symptoms of many conditions, including thiamine deficiency.

8. Delirium

Vitamin B1 deficiency can lead to delirium, a serious condition in which you experience:

• confusion
• reduced awareness of your environment
• an inability to think clearly