Vitamin B1 (Thiamine) Deficiency in Dogs

Key takeaways

Thiamine (vitamin B1) deficiency is an uncommon, but potentially serious condition in dogs resulting from inadequate intake, poor absorption, or excessive excretion of vitamin B1. 

• Symptoms of thiamine deficiency occur in three stages 

• Multiple body systems are affected during the induction phase with symptoms including poor appetite, vomiting, and weight loss 

• The second stage affects the nervous system with symptoms including reduced reaction to light, blindness, weakness, incoordination, and seizures 

• The final stage involves a rapid worsening of symptoms and is fatal within a few days

• Diagnosis is challenging and involves a combination of physical examination, blood work, and diagnostic imaging

• Treatment relies on supplementation of thiamine either as a single supplement, or by feeding a complete, balanced diet

• Prognosis depends on severity of the symptoms and speed of supplementation, most cases improve within days of supplementation

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A closer look: Vitamin B1 (Thiamine) Deficiency in Dogs

Thiamine is essential for the conversion of carbohydrates into a usable energy source, so symptoms of thiamine deficiency relate to failure of this mechanism. It is difficult to investigate and may be under-diagnosed as a disease. Prognosis with early diagnosis and timely supplementation is excellent. Most cases are not diagnosed until late in the disease process which may result in long term neurological deficits or death. Dogs with suspected thiamine deficiency require prompt veterinary attention

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Risk factors

Thiamine deficiency is a rare condition in dogs and is potentially fatal. Dogs eating primarily a homemade diet or commercially prepared raw diet are at higher risk for developing thiamine deficiency. Symptoms vary depending on the severity of deficiency. Symptoms in the early stages are usually non-specific and cases are rarely diagnosed at this stage. The critical and terminal stages progress rapidly.

Possible causes

Thiamine deficiency is the result of inadequate intake, poor absorption, or excessive excretion of vitamin B1. Inadequate intake is more common in home cooked diets as the levels of thiamine are not consistent. Deficiency is less common in traditional commercial diets but is still possible as thiamine is a delicate vitamin which is easily inactivated by the processing of commercial dog foods. Absorption of thiamine is sometimes reduced in cases of intestinal disease which may result in a deficiency in severe cases.

Thiamine is excreted through the kidneys and conditions such as kidney disease, or the use of medications which increase excretion such as diuretics, sometimes results in deficiency.

Main symptoms

Symptoms of thiamine deficiency are described in three stages; induction, critical, and terminal.

If the deficiency progresses to the terminal stage, it results in rapid progression and worsening of symptoms and death within a few days.

Testing and diagnosis

Diagnosis of thiamine deficiency is challenging as vitamin B1 is not routinely measured in blood work, and the normal ranges are not well described. Diagnosis involves:

  • Physical examination
  • Blood work

Specialized testing may include:

  • Blood lactate levels
  • Rarely, blood thiamine levels
  • Urine lactate levels
  • Brain MRI scan

Diagnosis often relies on history, clinical examination, symptoms, and response to supplementation.

Steps to Recovery

Treatment involves thiamine supplementation. Cases resulting from inadequate intake usually resolve with feeding a complete, balanced diet whereas other causes, or cases diagnosed later, require supplementation with injections of thiamine. Cases resulting from poor absorption or excessive excretion usually require supplementation alongside treatment of the underlying cause, such as management of intestinal or kidney disease.

Prognosis is good when the condition is recognised early. Improvement with thiamine supplementation is rapid with some improvement noticed within a few hours, and significant improvement within a week of feeding a balanced diet. Cases where diagnosis and supplementation are late in the disease can result in permanent neurological deficits or death.


Prevention of inadequate intake involves feeding a good quality, complete, commercial dog food diet. Routine supplementation is not required in most dogs. Thiamine is a delicate vitamin and can be easily lost in commercial diets as well as home made diets. Bags of dog food should be in date and undamaged to ensure correct nutrient levels are preserved. Canned foods are also more susceptible to thiamine deficiency.

Is Vitamin B1 (Thiamine) Deficiency in Dogs common?

Thiamine deficiency is rare in dogs but is more common in dogs fed a home cooked or commercially-prepared raw diet.

Typical Treatment

  • Vitamin B1 supplementation
  • Feeding a balanced diet
  • Treatment of intestinal disease
  • Treatment of kidney disease