Vitamin Deficiency And Type 2 Diabetes

Understanding type 2 diabetes

Causes of type 2 diabetes?

Type 2 diabetes is a condition where not enough of the hormone insulin is produced by the pancreas, or the insulin that is produced does not work effectively. The body’s cells become resistant to insulin and prevent insulin from working properly. The glucose is not absorbed by the cells to be used as energy, and this leads to increased levels of glucose in the bloodstream.1

Usually, type 2 diabetes is linked with having a family history of Type 2 diabetes, a sedentary lifestyle and being overweight. A poor diet also plays a role in the development of type 2 diabetes.2

Signs and symptoms

You will usually experience the following symptoms if you have type 2 diabetes:2

  • Frequent urination, especially at night
  • Thirst 
  • Fatigue 
  • Frequent development of thrush 
  • Itching around the genitalia
  • Blurry vision 


Diagnosis of type 2 diabetes can be done by several methods if an individual is experiencing the symptoms mentioned above. However, not all individuals may experience symptoms of type 2 diabetes in the beginning, and symptoms may only develop over several years. The following tests can determine the levels of glucose in the blood: 

  • Random glucose test (conducted at any time without the need for fasting)
  • Fasting glucose test (usually conducted after fasting overnight)
  • HbA1c test (provides an average blood glucose level over a 2-3 month period)

An HbA1c score of 48 mmol/mol or above diagnoses the patient with type 2 diabetes. However, anything below 48 mmol/mol is not excluded and is still classed as a high risk of developing type 2 diabetes.3


A high level of blood glucose over a long period of time can eventually cause damage to the body’s organs. Further complications include.4 

  • Foot damage
  • Poor blood flow resulting in prolonged healing of cuts and wounds 
  • Eye damage, also known as retinopathy
  • Damaged blood vessels may lead to heart attacks and strokes. 
  • Kidney problems, also known as nephropathy
  • Nerve damage, also known as neuropathy 
  • Sex-related problems in men and women 
  • Increased risk of developing cancer 
  • Dental problems such as gum disease and infections 

About vitamin deficiency

Causes of vitamin deficiency

Vitamin deficiencies can usually occur due to a lack of vitamin intake or due to medical conditions. 

Vitamin D deficiency can be caused by a lack of sunlight or a poor diet with a lack of vitamin D-rich foods such as red meat, liver, egg yolk, and oily fish.5

Vitamin A deficiency can be caused by a poor diet that is low in the following foods: cheese, milk, yoghurts, liver, oily fish and eggs.6

Vitamin B12 is usually caused by a lack of meat and dairy products in the diet.7  

Signs and symptoms

Individuals with a vitamin deficiency may experience the following symptoms:

Vitamin D deficiency:  

  • Fatigue
  • Bone pain
  • Muscle weakness
  • Depression
  • Anxiety 

Vitamin B12 deficiency: 

  • Weight loss 
  • Muscle weakness
  • Tingling in hands and feet 
  • Fatigue 
  • Mouth ulcers 

Vitamin A:

  • Night blindness
  • Infection
  • Skin irritation


As vitamin D helps to regulate the levels of phosphate and calcium in the body, a lack of vitamin D in the body can lead to a loss of bone density resulting in bone pain and bone deformities. Individuals with vitamin D deficiency can also be at a higher risk of type 2 diabetes; however, more research is required to understand the relationship between the two.8

Vitamin A deficiencies can lead to xerophthalmia, which is an eye disease. There can be different stages to this, and night blindness is one of them. Long-term deficiency can also lead to pneumonia and complications with the heart and immune system.9 

A lack of vitamin B12 can cause problems for the nervous system, such as memory loss, vision problems and loss of coordination. It can also lead to peripheral neuropathy (mainly in the legs) and temporary infertility.7

Vitamin deficiency and type 2 diabetes

Can vitamin deficiency trigger type 2 diabetes?

Vitamin D reduces inflammation and aids the secretion and sensitivity of insulin; therefore, vitamin D deficiency may contribute to insulin resistance and increase the risk of the development of type 2 diabetes.10,11,12 Usually, patients diagnosed with type 2 diabetes also have a slight deficiency in Vitamin D. It has been found that supplementation of vitamin D may help in insulin sensitivity and insulin production in patients with type 2 diabetes.13

Vitamin A is required to maintain pancreatic B-cells that store and release insulin. In patients with type 2 diabetes, where not enough of the hormone insulin is produced by the pancreas, there has been a link between Vitamin A deficiencies. Vitamin A supplementation may play a beneficial role in type 2 diabetes.14,15,16 

Patients with type 2 diabetes usually take metformin, a medication that lowers glucose production in the liver and improves insulin sensitivity. This medication has been associated with a deficiency in Vitamin B12.17 There is a link between Vitamin b12 deficiency in type 2 diabetes patients; however, there was no link found between Vitamin b12 deficiency and new on-set diabetes, concluding that patients with Type 2 diabetes may experience B12 deficiencies, but the deficiency is not the cause of type 2 diabetes.18

Treatment and prevention for vitamin deficiencies 

Choosing the best vitamins/supplement

Vitamin A supplements are available in the form of retinyl acetate or retinyl palmitate (Preformed Vitamin A), or beta-carotene (Provitamin A). You will also tend to find vitamin A in most multivitamin-mineral supplements. All the vitamins mentioned in the article, including vitamins B12 and D, can be obtained from your local pharmacy or drug store. Vitamin D can also be obtained from sunlight during the spring and summer seasons; however, during the winter we may be deficient and require supplementation.

Best foods to eat

Below is a list of the best foods to obtain vitamins A, D and B12. 

Foods rich in Vitamin A:19

  • Leafy green vegetables
  • Tomatoes
  • Red pepper 
  • Liver and liver products 
  • Milk
  • Eggs 
  • Fish 

Foods rich in Vitamin D: 

  • Fish 
  • Cod liver oil 
  • Dairy products fortified with Vitamin D 

Foods rich in Vitamin B12:

  • Meat 
  • Fish 
  • Dairy products 

When to seek medical attention

If you are experiencing any of the symptoms mentioned above, it is advised to consult your doctor and seek medical help. If symptoms worsen and become unbearable, please seek urgent care. 


Type 2 diabetes is a chronic metabolic disorder where the blood sugar levels become elevated. If you have type 2 diabetes, you may experience symptoms such as thirst, fatigue, dizziness and blurred vision. This chronic condition can cause long-term complications such as kidney disease, eye damage, blood vessel disease and neuropathy. Patients with type 2 diabetes have also been associated with vitamin deficiencies, a specific lack of vitamin b12, A, or D. 

Although there have been associations between vitamin deficiencies and Type 2 diabetes, there is not enough evidence to recommend high-dose supplementation to prevent or treat Type 2 diabetes. However, to avoid complications and symptoms caused by vitamin deficiency, it is advised to adhere to a nutrient-rich diet to maintain adequate levels of vitamin levels in the body.  


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  4. Complications of diabetes [Internet]. Diabetes UK. [cited 2022 Oct 23]. Available from:
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  7. Vitamins and minerals - B vitamins and folic acid [Internet]. 2017 [cited 2022 Oct 23]. Available from:
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  12. Szymczak-Pajor I, Śliwińska A. Analysis of association between vitamin d deficiency and insulin resistance. Nutrients [Internet]. 2019 Apr 6 [cited 2022 Oct 23];11(4):794. Available from:
  13. Lips P, Eekhoff M, van Schoor N, Oosterwerff M, de Jongh R, Krul-Poel Y, et al. Vitamin D and type 2 diabetes. J Steroid Biochem Mol Biol. 2017 Oct;173:280–5.
  14. Trasino SE, Benoit YD, Gudas LJ. Vitamin a deficiency causes hyperglycemia and loss of pancreatic β-cell mass. J Biol Chem [Internet]. 2015 Jan 16 [cited 2022 Oct 23];290(3):1456–73. Available from:
  15. Valdés-Ramos R, Ana Laura GL, Elina MCB, Donají BAA. Vitamins and type 2 diabetes mellitus. Endocr Metab Immune Disord Drug Targets [Internet]. 2015 Mar [cited 2022 Oct 23];15(1):54–63. Available from:
  16. Iqbal S, Naseem I. Role of vitamin A in type 2 diabetes mellitus biology: effects of intervention therapy in a deficient state. Nutrition. 2015 Aug;31(7–8):901–7.
  17. Pflipsen MC, Oh RC, Saguil A, Seehusen DA, Seaquist D, Topolski R. The prevalence of vitamin b12 deficiency in patients with type 2 diabetes: a cross-sectional study. J Am Board Fam Med [Internet]. 2009 Sep 1 [cited 2022 Oct 23];22(5):528–34. Available from:
  18. Liu L, Huang X, Wang B, Song Y, Lin T, Zhou Z, et al. Vitamin B12 and risk of diabetes: new insight from cross-sectional and longitudinal analyses of the China Stroke Primary Prevention Trial (Csppt). BMJ Open Diabetes Research and Care [Internet]. 2020 Oct 1 [cited 2022 Oct 23];8(1):e001423. Available from:
  19. Boston 677 Huntington Avenue, Ma 02115 +1495‑1000. Vitamin a [Internet]. The Nutrition Source. 2012 [cited 2022 Oct 23]. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Darija Golubovic

Bachelor's degree, Nutrition Sciences, The Manchester Metropolitan University, England

I graduated from Manchester Metropolitan University with a First Class in Nutritional Science BSc.
I aim to continue promoting health, wellbeing and fitness and influencing healthy food choices and sustainability.
Registered Associate Nutritionist delivering the NHS Diabetes Prevention Programme.

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