Vitamin B1 deficiency? Here are the causes and the solution.
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Leesduur: 5 min
Did you know that vitamin B1 (thiamine) was one of the very first vitamins discovered? Without enough B1, your energy metabolism literally grinds to a halt. A serious deficiency, also known as beriberi, is thankfully rare in the Netherlands.
However, a deficiency can creep up, especially in people who drink a lot of alcohol or follow a limited diet. I'll show you how to recognize a deficiency, what causes it, and what you can do about it.
A vitamin B1 deficiency often develops gradually and causes symptoms such as fatigue, concentration problems, tingling or muscle weakness, especially noticeable in the nervous system, heart and muscles.
Important causes include excessive alcohol consumption, a one-sided diet, gastric reduction surgery, chronic diseases or pregnancy with heavy vomiting, which disrupt the absorption and storage of B1.
Deficiencies can usually be easily addressed through supplements and a diet containing whole grains, legumes, nuts, meat, and fish; medical monitoring is important if there is an increased risk.
Symptoms of a vitamin B1 deficiency
B1 keeps several links in your energy chain running. If this "key" is missing (as in a shortage), the engine runs at half power.
And you notice this first in tissues with high energy requirements, such as your nervous system (tingling, concentration problems) and heart/muscles (muscle weakness and, in more serious deficiency, shortness of breath).
A B1 deficiency usually develops gradually. The initial symptoms are often vague, making them easily missed:
- Fatigue and low energy
- Decreased appetite
- Irritability or despondency
- Numbness or tingling in hands and feet
- Muscle weakness
- (Often) some brain fog or difficulty focusing
In severe deficiency it can lead to beriberi , a disease caused by a severe deficiency of thiamine, or even Korsakoff's syndrome in alcoholism. (1)(2)
The most common causes of thiamine (B1) deficiency
In the Netherlands and other Western countries, alcohol abuse is by far the leading cause of vitamin B1 deficiency. However, other factors can also play a role, although they are less common.
These are the most important causes in a row:
- Alcohol Abuse - Too much alcohol causes your body to absorb B1 less effectively and store it in the liver. This can eventually lead to nerve damage and memory problems. (3)
- Malnutrition - If you eat few whole grains or legumes, or mainly white rice and processed foods, you may not get enough B1. This is more common worldwide in cases of poverty or very one-sided diets. (4)
- Gastric sleeve surgery - After gastric sleeve surgery, the body absorbs much less B1. This leads to a deficiency in 15–30% of patients. (5)
- Pregnancy - Excessive vomiting in the early months of pregnancy can quickly deplete B1 stores, especially between weeks 10 and 15. (6)
- Chronic diseases and medications – People on kidney dialysis, diabetes, or who use water pills (diuretics) lose more B1 and are therefore more likely to become deficient. (7)
Want to quickly supplement your B1 deficiency? Follow my step-by-step plan.
Fortunately, you can easily replenish your deficiency. Start with the following 4 steps:
- Supplements – Do you really have a deficiency? Then a supplement is the fastest way to replenish your supply. Often, a single B1 capsule or a good B complex will work well. For a severe deficiency, a doctor may prescribe higher doses.
- Supplementing your diet – Next, it's all about your daily diet. Choose whole-wheat bread, brown rice, oatmeal, legumes, nuts, meat, and fish. I always make sure I have a bag of nuts with me on the go and regularly snack on some B1 that way. I also often have oatmeal for breakfast.
- Improve your lifestyle – Do you drink alcohol often? Then your B1 stores will be depleted very quickly. You'll often notice a difference quickly by drinking less. Also, avoid crash diets or a very limited menu.
- Medical support – Have you had gastric bypass surgery, are experiencing frequent vomiting, or have a chronic illness? Have your B1 levels checked regularly.
How much B1 do you need daily?
Count on about 1 mg of B1 per day . Exactly how much you need depends on how much you eat in a day. This amount of 1 mg is based on an average energy intake of 2000 kcal per day. (8)(9)
Are you pregnant? Then you need a little more, about 1.4 mg per day .
Good to know : There is no set upper limit for B1, because B vitamins are water-soluble, so you simply pee out any excess.
My personal advice
If I suspect a B1 deficiency, I start with a modest dose. By that, I mean about 1–3 mg per day . This can be taken on its own (just B1), but I usually choose a B-complex supplement as a "safety net" to keep the B vitamins in balance.
I have a few tips for you:
- It is best to take B vitamins with a meal.
- A low, regular dose works better than an occasional high dose.
- And less alcohol helps your body use them optimally.
Furthermore, I advise you to pay attention to the composition of a B-complex:
- B1 as thiamine HCl (stable, easily absorbable form, widely used in tablets and capsules)
- B6 preferably ≤ 5 mg/day (higher doses can cause nerve complaints)
- B3 as nicotinamide/niacinamide (no flush)
- Folate as 5-MTHF (active form)
- B12 in active forms (methyl- or adenosylcobalamin; may be slightly higher in dose)
Are you unsure about your symptoms? Or are you pregnant or chronically ill? Then it's always best to consult your doctor first.
Ebrina van der Bijl
Ebrina is a nutritionist with a deep commitment to healthy eating and a sustainable lifestyle, based in beautiful Portugal. Her passion for natural and organic products is at the heart of her work. With a background in Nutrition & Dietetics and experience in product development and writing, she translates complex scientific information into practical advice for a balanced lifestyle.
Sources used
- The role of thiamine deficiency in alcoholic brain disease. (2003). PubMed. https://pubmed.ncbi.nlm.nih.gov/15303623/
- Julian, T., Glascow, N., Syeed, R., & Zis, P. (2018). Alcohol-related peripheral neuropathy: a systematic review and meta-analysis. Journal Of Neurology, 266(12), 2907–2919. https://doi.org/10.1007/s00415-018-9123-1
- Bahardoust, M., Eghbali, F., Shahmiri, SS, et al. (2022). B1 vitamin deficiency after bariatric surgery, prevalence, and symptoms: a systematic review and meta-analysis. Obesity Surgery, 32(9), 3104–3112. https://doi.org/10.1007/s11695-022-06238-9
- Whitfield, K.C., Bourassa, MW, Adamolekun, B., et al. (2018). Thiamine deficiency disorders: diagnosis, prevalence, and a roadmap for global control programs. Annals of the New York Academy of Sciences, 1430(1), 3–43. https://doi.org/10.1111/nyas.13919
- Bahardoust, M., et al. (2022). B1 vitamin deficiency after bariatric surgery, prevalence, and symptoms: a systematic review and meta-analysis. Obesity Surgery, 32(9), 3104–3112. https://doi.org/10.1007/s11695-022-06238-9
- Whitfield, K.C., et al. (2018). Thiamine deficiency disorders: diagnosis, prevalence, and a roadmap for global control programs. Annals of the New York Academy of Sciences, 1430(1), 3–43. https://doi.org/10.1111/nyas.13919
- Sedhai, Y.R., Shrestha, D.B., Budhathoki, P., et al. (2021). Effect of thiamine supplementation in critically ill patients: A systematic review and meta-analysis. Journal of Critical Care, 65, 104–115. https://doi.org/10.1016/j.jcrc.2021.05.016
- Nutrition Center. (nd). Vitamin B1. Retrieved August 26, 2025, from https://www.voedingscentrum.nl/encyclopedie/vitamine-b1
- EFSA Panel on Dietetic Products, Nutrition and Allergies. (2016). Dietary reference values for thiamin. EFSA Journal, 14(12), e04656. https://doi.org/10.2903/j.efsa.2016.4656
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