Thiamine

What is thiamine?

Thiamine, also known as vitamin B1, is a water-soluble vitamin essential for turning food into energy. It’s mainly used to prevent and treat thiamine deficiency, including more serious conditions caused by long-term lack of this vitamin[1].  

What is thiamine used to treat?

Thiamine is used to treat[1]: 

• Beriberi – a condition caused by thiamine deficiency that affects the heart, muscles, and nervous system 

• Wernicke-Korsakoff syndrome (WKS) – a serious brain disorder often linked to alcohol misuse 

• Nerve or brain damage related to alcohol use 

• It may also be used occasionally for menstrual cramps and certain inherited metabolic disorders 

How does thiamine work?

Thiamine helps your body convert carbohydrates into energy, which is especially important for the brain, muscles, and nerves. It acts as a coenzyme in glucose metabolism, helping cells function properly and supporting nerve signals and muscle contractions[1]. 

Who can take thiamine?

Thiamine is generally safe and suitable for most people, including children and pregnant or breastfeeding women – when taken at recommended doses. However, it may not be suitable for people who[1]: 

• Have an allergy to thiamine or any ingredients in the supplement 

• Have rare hereditary conditions like fructose intolerance (as some thiamine products may contain sugars) 

• Are due to have blood tests or scans imminently  

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].

What is the typical dosage of thiamine?

Thiamine comes as 50mg or 100mg tablets, 100mg slow-release tablets, and 100mg in 5ml solution. The dose depends on what thiamine is being used to treat[1]: 

• Mild deficiency: 25 to 100mg per day 

• Severe deficiency or WKS: from 100mg per day 

Always follow the instructions provided by your doctor or the label on the packaging. 

How do you take thiamine?

Thiamine is usually taken by mouth as tablets or capsules. In more serious cases, it may be given as an injection in a clinical setting. For best results[1]: 

• Take it with or after food to help absorption 

• Swallow tablets whole with water unless otherwise directed 

Can you stop taking thiamine?

If you’re taking thiamine to correct a short-term deficiency, you can usually stop once your doctor says it’s no longer needed. However, if you’re on a high dose or taking it for a chronic condition, talk to your doctor before stopping[1]. 

What do you do if you take too much thiamine?

Thiamine is generally safe, even in high doses, as excess amounts are excreted in urine[1]. If you feel unwell or are concerned after taking too much, contact a doctor or pharmacist. 

What if you forget a dose of thiamine?

If you forget to take a dose[1]: 

• Take it as soon as you remember 

• If it’s nearly time for your next dose, skip the missed dose and take the next one at the usual time 

• Do not take a double dose to make up for a missed one 

What medicines can you and can’t you take with thiamine?

Thiamine is safe to take with most medicines, but there are a few interactions to be aware of. You should speak to your doctor or pharmacist if you’re also taking[1]: 

• Chemotherapy medicines 

• Diuretics (like furosemide) 

• Antacids, which may reduce thiamine absorption 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of thiamine?

Side effects from thiamine are rare. Most people tolerate it well. However, in some cases it may cause[1]: 

• Nausea  

• Diarrhoea 

• Stomach ache 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis), the symptoms of which are below. You should call 999 or visit A&E immediately if you believe this is happening[1]. 

• Difficulty breathing 

• Tightness in throat and chest 

• Swelling of the tongue or throat 

• Feeling faint or dizzy 

• Blue/grey skin or lips 

• Loss of consciousness 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2].

Frequently asked questions about thiamine

Can I take thiamine long-term? 
You can take thiamine long-term if advised by your doctor, particularly for ongoing conditions like chronic alcohol use or absorption disorders[1]. 

Is thiamine the same as vitamin B complex? 
Not quite. Thiamine is one of the B vitamins, but B complex supplements usually contain several B vitamins together, not just B1[1]. 

Can I get enough thiamine from food? 
Yes, most people can get enough from foods like whole grains, pork, legumes, and fortified cereals. However, alcohol misuse or certain medical conditions may reduce how well your body absorbs it[1]. 

Is thiamine safe during pregnancy? 
Yes, in normal recommended amounts. Higher doses should only be taken if prescribed by a doctor[1]. 

Can I drink alcohol while taking thiamine? 

It’s a good idea to avoid alcohol if taking thiamine for vitamin B1 deficiency. This is because heavy or long-term drinking can stop your body from absorbing it[1].  

For the official NHS guide for thiamine, visit their website.