Guide To The Symptoms Of A Thiamine Deficiency

February 25, 2024

A thiamine deficiency means an individual has low levels of vitamin B1 (thiamine) in their body. Thiamine is an essential vitamin that supports many functions of the body. It is critical in converting food into energy and just about all cells use it to function properly. The only way to get thiamine is to ingest it because the body cannot produce it. There are various reasons individuals may experience a thiamine deficiency, including old age, diabetes, bariatric surgery, and alcohol dependency. Thiamine deficiency patients will suffer from various symptoms that can mimic other conditions but should be examined either way.

Shortness Of Breath

Thiamine deficiency can cause problems with the heart and making it beat too slow. Putting this kind of stress on the heart can result in shortness of breath and fatigue. Just like many other symptoms of a thiamine deficiency can be caused by various reasons, being short of breath can be indicative of other illnesses. It is important, then, for doctors to evaluate this with other symptoms patients might be having.

A thiamine deficiency can also lead to heart failure because the heart is working too hard to pump the blood through the body. When this happens, fluid can accumulate and make it harder to breathe and results in being short of breath. The extra work being forced on the heart can also contribute to other symptoms, like fatigue.

Blurry Vision

It is important if a patient experiences blurry vision, and there are other contributing factors, that they have their thiamine levels checked. A severe thiamine deficiency can cause the optic nerve to swell, which can cause problems with the patient's vision, such as blurriness, and can even result in the loss of vision. However, there is a significant chance vision problems will lessen when the thiamine deficiency is corrected. Vision issues such as blurry vision can also be linked to problems in the brain because the thiamine deficiency can affect the nerves and other parts of the brain.

Tingling In The Arms And Legs

Tingling in the arms and legs is called paresthesia, which is different from when individuals experience their limbs 'going to sleep' because they have been put in an awkward position that cuts off blood flow. The sensation of 'pins and needles'; goes away as circulation is returned to the area. Paresthesia is more concerning. A thiamine deficiency can damage the peripheral nerve, and if the peripheral nerve is damaged, it can make it difficult to walk or hold onto things. Paresthesia in a leg makes it incredibly difficult for individuals to walk. It is important for patients with ongoing episodes of paresthesia to consult a doctor, especially if they are experiencing other symptoms.

Fatigue And Irritability

Many illnesses and diseases cause fatigue and irritability, so it is easy to dismiss it and not consider thiamine deficiency. A thiamine deficiency can cause fatigue to come on suddenly but can also occur over an extended period. The body works hard to convert food into energy, and when there is a deficiency of thiamine, which is essential in this conversion, the body is working extra hard. This can lead to fatigue, and along with fatigue can come irritability. When the body is fatigued, it is more difficult to remain in a good state of mind. Just like fatigue, irritability can be associated with many different conditions, but when they are present alongside other symptoms on this list, a thiamine deficiency is a real possibility.

Lack Or Loss Of Appetite

One of the most common symptoms of a thiamine deficiency is a lack or loss of appetite. It seems the part of the brain that affects appetite is altered when there is a thiamine deficiency. When individuals have a deficiency in thiamine, their body thinks it is full or satisfied when it is not. This causes less food to be eaten, weight loss, and potential eating disorders. If an individual's body is telling them it does not need food because it is full, the individual will be less inclined to eat.

Conversely, there are times the body cannot seem to be satiated and individuals will not be able to get enough food. The problem with a thiamine deficiency is it affects the functioning of the satiety center in the brain and causes problems of being full to being hungry at an extreme level.

Swelling In The Legs

Swelling in the legs may be indicative of a thiamine deficiency. This symptom is related to the cardiovascular involvement that occurs with a shortage of thiamine. A thiamine deficiency triggers a cascade of events, including the dilation of blood vessels in an affected individual's limbs. When this occurs, the renin-angiotensin-aldosterone system in the body leaps into action. The detection of volume loss in the blood vessels causes the affected individual's kidneys to react by retaining salt, which leads to the retention of fluids. This mechanism in the body increases blood pressure to prevent ischemic events.

However, adverse symptoms can occur as a result of the overactivation of such homeostatic mechanism. Individuals affected by a thiamine deficiency retain significantly higher amounts of salt and fluid in their body, which eventually results in fluid overload. Excess fluid in circulation can be dangerous, so the fluid begins to leak through the blood vessel walls instead of continuing to accumulate in circulation. This mechanism is what causes swelling in the legs due to the force of gravity on the tissues containing this excess fluid.

Weight Loss

Thiamine deficiency patients may exhibit weight loss as a symptomatic manifestation of their condition. Carbohydrates are a form of dietary nutrient the body utilizes to produce energy the cells are able to utilize. Weight loss may occur in a thiamine deficiency because the brain's mechanism of mediating low energy states in affected individuals called AMP-activated protein kinase (AMPK) becomes impaired. AMPK in the hypothalamus acts to restore the balance of energy in the body through increasing the production of glucose, stimulating feeding behavior, and stopping thermogenesis to slow the output of energy.

However, a thiamine deficiency inhibits the action of AMPK in the hypothalamus, which cripples the mechanism the body uses to keep a balance between energy expenditure and energy intake. Without this balance, the patient will not have an appetite triggered by the AMPK mechanism, and the expenditure of energy at rest will not decrease. This negative energy balance burns away any calories and extra fat around the body during energy-making processes, resulting in obvious weight loss and anorexia in some cases.

Compromised Reflexes

Compromised reflexes may be a symptom manifestation of thiamine deficiency. Because thiamine is critical for the metabolism of carbohydrates and proteins, a lack of it means these metabolic processes do not occur as much. As a side effect of this malfunction, the products of carbohydrate synthesis called pyruvic acid and lactic acid accumulate in the tissues and cause the progressive degeneration of nerve cells. The long nerves in the legs are typically affected first, and the long nerves of the arms follow. Because the nerves play a large role in the reflexes, damage to these nerves can result in a loss or reduction of the reflexive functions.

Additionally, the wasting of muscle that occurs in individuals who have a thiamine deficiency due to inadequate energy production can contribute to the compromise of reflexes. The reason for this is because the muscle is the tissue that produces movement of the limb in a reflex. Both the muscular and neural components of the reflexes must be functional in order to produce a reflex movement in response to stimuli.


Individuals who experience delirium may be affected by a deficiency of thiamine. Thiamine is an important vitamin that helps facilitate the conversion of dietary nutrients into cellular energy the body can use. These processes require the use of certain enzymes that depend on the presence of thiamine to work correctly. As a result, there is a reduction in the activities of these enzymes that effectively begins a cascade of metabolic events that compromise significant amounts of energy. Certain tissues in the brain have greater metabolic requirements than other parts. The absence of energy and thiamine in these demanding tissues results in neuronal death. When this process occurs in certain parts of the brain, the patient can experience episodes of delirium.

Additionally, a thiamine deficiency commonly results in increased cardiac output and an elevated resting heart rate. Both of these factors over time can result in reduced heart function. When the heart cannot pump efficiently enough or blood pressure becomes too low, not enough oxygen is delivered to the tissues in the brain. This mechanism can also result in an affected individual's delirium.

Nausea And Vomiting

Nausea and vomiting is an uncommon symptom manifestation in a thiamine deficiency. The mechanism behind the occurrence of this symptom is similar to what adversely affects the reflexes. A build-up of lactic acid and pyruvic acid in the blood can cause inflammation in the fibers of a nerve the brain uses to communicate with the digestive tract. This nerve is called the vagus nerve, and it is responsible for the stimulation of involuntary movements in the stomach, esophagus, and most of the intestines. These movements help food travel through the gastrointestinal tract.

When the vagus nerve becomes inflamed and swollen, it can cause abnormalities in the transmission of signals between the brain and muscles that produce these movements in the stomach and esophagus. When these abnormalities include a spasmodic misfiring of nerve impulses, the esophagus and or stomach can move too much. This abnormal movement can cause the patient to feel nauseated and or vomit as a result of their thiamine deficiency.

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