B1 is a vitamin your body uses to turn food into energy

B1, also called thiamine, is a water-soluble vitamin that helps your cells convert carbohydrates, fats, and proteins into usable energy. It also supports nerve function and helps your heart work properly. Unlike fat-soluble vitamins that your body can store, B1 dissolves in water, so your body doesn't keep reserves — you need to get it regularly from food or supplements.

Most people in developed countries get enough B1 from their diet, but certain groups are at higher risk of deficiency. This includes people with alcohol use disorder, those with digestive conditions that affect nutrient absorption, and people taking dialysis for kidney disease. Severe B1 deficiency is rare but serious; it can cause a condition called beriberi, which damages nerves and the heart.

Key Takeaways

  • B1 helps your body convert food into energy and supports nerve and heart function.
  • Your body does not store B1, so you need a regular dietary source or supplementation.
  • Most people meet their B1 needs through everyday foods like whole grains, pork, legumes, and fortified cereals.
  • Certain medical conditions and medications can interfere with B1 absorption or increase your need for it.
  • A healthcare provider can test B1 levels if you have symptoms like fatigue, nerve pain, or heart problems.

Where B1 comes from in food

B1 is found in both animal and plant sources. Pork is one of the richest natural sources, along with organ meats like liver and kidney. Plant-based sources include whole grains, legumes (beans and lentils), nuts, and seeds. Many breakfast cereals and breads are fortified with B1, which means the vitamin is added during manufacturing — this is a reliable way to meet your daily need if you eat these foods regularly.

The amount of B1 in food varies depending on how it is processed. Whole grains contain more B1 than refined grains because the vitamin is concentrated in the outer layers that are removed during refining. This is why white bread and white rice have less B1 than whole wheat bread and brown rice, unless they have been fortified.

How much B1 you need each day

The recommended daily amount of B1 varies by age and sex. Adult men need 1.2 milligrams per day, and adult women need 1.1 milligrams per day. Pregnant and breastfeeding women need slightly more — 1.4 milligrams per day. Children need less, ranging from 0.5 to 1.0 milligrams depending on their age.

These amounts are set by the National Institutes of Health and are based on what most healthy people need to prevent deficiency and support normal body function. If you have a medical condition that affects nutrient absorption or take certain medications, your healthcare provider may recommend a different amount.

Who is at risk for B1 deficiency

People with alcohol use disorder are at the highest risk for B1 deficiency because alcohol interferes with how your body absorbs and stores the vitamin. Chronic heavy drinking can deplete B1 stores quickly, even if someone is eating adequate amounts. This is why B1 supplementation is often part of treatment for alcohol withdrawal.

Other groups at higher risk include people with digestive disorders like celiac disease, Crohn's disease, or cystic fibrosis, which affect nutrient absorption in the intestines. People undergoing dialysis for kidney disease lose water-soluble vitamins like B1 during treatment. Older adults sometimes have lower B1 intake due to changes in appetite or difficulty chewing. People taking certain medications, including some diuretics and anticonvulsants, may need more B1 because these drugs interfere with absorption or increase how quickly the body uses it.

Signs that you might not be getting enough B1

Early signs of B1 deficiency can be subtle and include fatigue, weakness, and difficulty concentrating. Some people experience tingling or numbness in the hands and feet, or muscle pain. Mood changes like irritability or depression can also occur. These symptoms are not specific to B1 deficiency — they can have many causes — so they should be evaluated by a healthcare provider.

Severe B1 deficiency causes a condition called beriberi, which has two forms. Wet beriberi affects the heart and can cause fluid buildup, shortness of breath, and an irregular heartbeat. Dry beriberi affects the nervous system and causes nerve damage, muscle weakness, and difficulty walking. Wernicke-Korsakoff syndrome is another serious condition linked to severe B1 deficiency, usually seen in people with long-term alcohol use disorder; it causes confusion, memory problems, and coordination difficulties. These severe forms are rare in developed countries but require when ready medical attention.

B1 supplements and when they might be recommended

B1 supplements come in several forms: thiamine hydrochloride (the most common), thiamine mononitrate, and benfotiamine (a fat-soluble form that some research suggests may be absorbed differently). Supplements are available as tablets, capsules, and injections. Over-the-counter supplements typically contain 1.5 to 500 milligrams per dose, while prescription injections are used when someone cannot absorb B1 through the digestive system or needs rapid correction of severe deficiency.

A healthcare provider might recommend B1 supplementation if you have a condition that affects absorption, take medications that interfere with B1, have symptoms of deficiency, or are at high risk due to diet or medical history. Injections are usually reserved for people with severe deficiency or those who cannot take oral supplements. Because B1 is water-soluble, excess amounts are excreted in urine, so toxicity from too much B1 is not a concern — but this also means taking more than you need does not provide extra benefit.

How to talk with your healthcare provider about B1

If you think you might not be getting enough B1, start by describing your symptoms to your doctor — fatigue, nerve pain, heart palpitations, or mood changes. Mention any digestive conditions, medications you take, or dietary restrictions that might affect B1 intake. If you drink alcohol regularly or have a history of heavy drinking, tell your provider, as this significantly increases deficiency risk.

Your healthcare provider can order a blood test to measure B1 levels, though this test is not routine and is usually done only if deficiency is suspected. They can also review your diet and medications to identify whether you are likely getting enough B1 from food. If supplementation is recommended, your provider can advise on the right dose and form for your situation and monitor whether symptoms improve.

Frequently Asked Questions

Can I get too much B1 from food or supplements?

No. B1 is water-soluble, so your body excretes excess amounts in urine rather than storing them. Even high-dose supplements do not cause toxicity. However, taking more than you need does not provide additional health benefits.

Does B1 give you energy?

B1 helps your body convert food into energy, but it does not provide energy itself. If you already get enough B1 from food, taking more will not boost your energy. If you are deficient, supplementation can restore normal energy levels by allowing your cells to use food properly.

What medications interfere with B1 absorption?

Some diuretics, anticonvulsants, and medications used to treat tuberculosis can reduce B1 absorption or increase how quickly your body uses it. If you take any long-term medications, ask your healthcare provider whether B1 intake is a concern for you.

Is B1 deficiency common?

In developed countries, B1 deficiency is uncommon in the general population because many foods are fortified and most people eat a varied diet. It is more common in people with alcohol use disorder, certain digestive conditions, or those on dialysis. Globally, deficiency is more prevalent in areas where people rely heavily on white rice without fortification.

Can I take B1 with other B vitamins?

Yes. B vitamins work together in many body processes, and taking a B-complex supplement that includes B1 along with other B vitamins is safe and common. In fact, if you are deficient in one B vitamin, you may be low in others as well.