Sometimes, patients fear they have a serious complication when they report symptoms like confusion, fatigue, vision changes and worse, memory problems. They may even do all sorts of tests without realising that one possible but often overlooked cause could be a deficiency in vitamin B1, also known as thiamine.Thiamine is a water-soluble B vitamin that plays a key role in the body’s ability to convert carbohydrates into energy. It’s essential for the proper functioning of the nervous system, brain, muscles and heart. The body can’t produce thiamine on its own and stores very little, so it needs to be obtained regularly from food or supplements.What are symptoms of thiamine deficiency?Thiamine deficiency can affect many systems in the body but it most commonly impacts the brain and nervous system. Symptoms may include:Short-term memory lossMental confusion or disorientationDifficulty concentratingIrritability or mood changesFatigue or muscle weaknessPoor coordination or balanceBlurred vision or rapid eye movementsIf left untreated, severe deficiency can lead to Wernicke’s encephalopathy, a medical emergency characterised by confusion, loss of muscle coordination and eye movement abnormalities. In some cases, this progresses to Korsakoff syndrome, a chronic memory disorder.How to test for deficiencies?While blood tests can assess thiamine levels, they may not always be reliable or readily available, especially in resource-scarce settings. Some tests, like the transketolase activity test, indirectly assess thiamine status, but even these can be affected by other factors.Who is at risk?Thiamine deficiency is more common in certain groups, especially those with:Chronic alcohol use – Alcohol interferes with thiamine absorption and use.Low dietary intake – Diets high in processed foods and low in whole grains.Older age – Reduced absorption and higher requirements.Diuretic use – These medications increase thiamine loss through urine.Diabetes – Some studies suggest a link between low thiamine and blood sugar metabolism.Certain medical conditions – Conditions like gastrointestinal disorders, Celiac disease and post-bariatric surgery recovery can impair thiamine absorption.How to get enough thiamine?Story continues below this adMost people can meet their thiamine needs through a balanced diet. The recommended daily intake for adults is: 1.1 mg/day for women and 1.2 mg/day for men.What are good sources of thiamine?You would find thiamine in whole grains (brown rice, oats, whole wheat), legumes (lentils, beans), meat, sunflower seeds, nuts and peas, fortified cereals and breads. Highly processed foods, such as white rice and white bread, lose most of their thiamine during manufacturing unless they are fortified.Should you take a supplement?People in at-risk groups or those with signs of deficiency may benefit from supplementation. Thiamine is widely available as an individual supplement or as part of a B-complex. It is generally safe, as excess amounts are excreted in urine.In mild deficiency, low doses (5–30 mg daily) may be effective. In more severe cases or in clinical settings, higher doses are used under medical supervision. Always consult a healthcare provider before starting high-dose supplementation, especially if you have underlying health conditions.Story continues below this adWhile uncommon in severe form, mild thiamine deficiency is likely underdiagnosed, especially in older adults or those with poor diets. If you’re experiencing ongoing neurological symptoms, it’s worth discussing the possibility of thiamine deficiency with your healthcare provider.(Dr Chatterjee is senior consultant, internal medicine, Indraprastha Apollo Hospital, New Delhi)