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    Blood tests for vitamin and mineral deficiencies

    On this page
    1. What are vitamins and minerals?
    2. Different types of vitamins and minerals
    3. Minerals
    4. What are the main causes of vitamin and mineral deficiency?
    5. What are the signs and symptoms of a vitamin deficiency?
    6. How are vitamin and mineral deficiencies tested for?
    7. Our at-home blood tests

    Reviewed by Dr Bhavini Shah

    This article will talk through the roles of vitamins and minerals in body. We then discuss the signs and symptoms of deficiencies, and how you might get checked for them.  

    blood tests for vitamin deficiencies

    What are vitamins and minerals?

    Vitamins and minerals are nutrients your body needs in small amounts. They are needed to make sure you stay healthy and for your body to work properly. Most of us get the vitamins and minerals we need through a balanced diet, but some people may need to take supplements.

    Different types of vitamins and minerals

    Vitamin A

    Vitamin A is also known as retinol. It’s responsible for important functions, including: 

    • Helping the immune system work properly
    • Supporting your vision in dim light
    • Keeping your skin healthy

    Vitamin A can be found in dairy products, eggs, oily fish and liver.

    B vitamins and folic acid

    There are eight B vitamins in total. B vitamins support enzymes in a range of processes, including the release of energy from carbohydrates and transporting oxygen around the body.

    The natural form of vitamin B9 is folate. It is also added to foods and sold as a supplement as folic acid. Folate, or folic acid, is particularly important because it breaks down a substance (homocysteine) that can have harmful effects in high amounts. Folate is also essential in producing healthy red blood cells, and in supporting growth – for example, during pregnancy and foetal development.

    Foods containing folate include:

    • Chickpeas and kidney beans
    • Liver (but not to be eaten during pregnancy)
    • Cereals fortified with folic acid
    • Broccoli, brussels sprouts, peas and leafy green vegetables

    Vitamin C

    Vitamin C is also known as ascorbic acid. Vitamin C plays an important role in:

    • Protecting cells
    • Maintaining healthy blood vessels, skin, cartilage and bones
    • Supporting wound healing  

    A severe vitamin C deficiency is called scurvy.  

    You can find vitamin C in:

    • Citrus fruits, such as oranges
    • Peppers
    • Strawberries and blackcurrants
    • Broccoli
    • Brussels sprouts and broccoli
    • Potatoes  

    Vitamin D

    Vitamin D helps regulate the levels of calcium and phosphate in the body. Calcium and phosphate support healthy bones, teeth and muscles. If you don’t get enough vitamin D, you may develop a condition called osteomalacia, causing bone pain.  

    You can find vitamin D in:  

    • Egg yolks
    • Red meat
    • Liver
    • Oily fish
    • Some cereals are fortified with vitamin D

    Vitamin E

    Vitamin E helps keep our skin and eyes healthy. It also supports the immune system. You can find vitamin E in:

    • Plant oils
    • Nuts and seeds
    • Wheatgerm in cereals 

    Although rare, vitamin E deficiency can lead to nerve and muscle damage, and muscle weakness. A weakened immune system is also a sign.

    Vitamin K

    Vitamin K is a group of vitamins. They are important in blood clotting and healing wounds. You can find vitamin K in:

    • Vegetable oils
    • Cereal grains
    • Leafy green vegetables  

    A vitamin K deficiency can lead to excessive bleeding, for example, from a minor injury. Wounds also take longer than usual to heal.



    Calcium is important in keeping bones healthy, regulating muscle contractions (including our heartbeat) and blood clotting.

    A lack of calcium can lead to osteoporosis (a condition causing weak bones) and osteomalacia (a condition causing bone pain).

    You can find calcium in:

    • Dairy foods
    • Leafy green vegetables
    • Bread and foods made with fortified flour  


    Iodine is a mineral, rather than a vitamin. It supports in the creation of thyroid hormones. These hormones keep cells and the metabolic rate (the amount of energy burned) healthy.

    You can find iodine in:

    • Dairy products
    • Eggs
    • Shellfish and sea fish 

    A lack of iodine can result in hypothyroidism (an underactive thyroid) although this is usually caused by an autoimmune disorder.


    Iron is a mineral. It is important in making haemoglobin – this is a protein that carries oxygen around the body.

    You can find iron in:

    • Turkey and chicken
    • Lean red meat
    • Liver (but this is not suitable for pregnant women because of its high vitamin A content)
    • Fish – particularly oily fish 

    What are the main causes of vitamin and mineral deficiency?

    The main causes of vitamin and mineral deficiency include:

    • Poor nutrition
      • Not eating enough food
      • Not eating enough of the right foods 
    • An inability to absorb nutrients causes by an underlying condition – for example, Crohn’s disease or celiac disease. 

    What are the signs and symptoms of a vitamin deficiency?

    Signs and symptoms of a vitamin deficiency will depend on what vitamin you are deficient in. The table below provides a summary for the vitamins and minerals talked about in this article.

    Signs and symptoms
    Vitamin A
    Changes in vision and poor/no vision at night.
    B vitamins and folic acid 
    Tiredness; lack of energy; pins and needles; sore and red tongue; mouth ulcers; vision problems; muscle weakness, depression; anxiety; confusion; and problems with memory and understanding.
    Vitamin C
    Scurvy, with symptoms including, feeling tired and weak; feeling irritable and sad; joint and muscle pain; swollen and bleeding gums; red or blue spots on the skin; and skin that bruises easily.
    Vitamin D
    Bone pain, caused by a condition called osteomalacia.
    Vitamin E
    Vitamin E deficiency is a very rare condition – it is not caused by diet. It is usually caused by an underlying condition, such as a fat metabolism disorder. People may experience muscle damage and a weakened immune system.
    Vitamin K
    A deficiency is rare but may occur in people taking certain medications. Signs include bleeding; a longer blood clotting time (measured by your doctor); a low bone density (osteopenia); and weakened bones (osteoporosis). 

    An unexpected fracture or loss of a tooth is sometimes the first sign.

    Other symptoms include difficulty swallowing; faintness, anxiety; low blood pressure; stomach cramps; brittle nails and hair; hip and spine pain; loss of height; and brittle hair and nails.

    A severe calcium deficiency could cause muscle spasm or cramping; tingling of the mouth and fingers; seizures and tremors. 

    IodineSwelling of the thyroid gland (goitre); tiredness; weight gain; constipation; dry skin; aches; and feeling cold.
    IronSigns of iron deficiency include tiredness; low energy; shortness of breath; a noticeable heartbeat; paler than usual skin; and headaches. Blood loss is also a cause of iron deficiency and should be followed up with your GP. 

    How are vitamin and mineral deficiencies tested for?

    The first step in testing for a vitamin or mineral deficiency is usually a blood test. You can do finger prick blood tests at home, but depending on your symptoms, it might be better to visit your GP and have the test done there.

    You may be recommended treatment based on the findings. If your test shows that you’re low in vitamin D, you may be offered a supplement.

    Depending on your results, you may need further tests. For example, if you’re low in vitamin B12 or folate, your GP may want to rule out an auto-immune condition.

    Vitamin supplements should not be needed in a healthy person with a varied diet. They can also be harmful if taken in excess. If you’re feeling generally unwell and thinking of taking a supplement, it’s best to talk to your doctor first. 

    Our at-home blood tests

    LloydsPharmacy Online Doctor’s blood tests can be done at home. Our general health blood test checks your vitamin D levels as well as your thyroid function. You can also use it to understand your diabetes risk, liver function, and thyroid function. 

    An at-home blood test may provide a good starting point for understanding your health’s big picture. However, if you’re worried about something or feeling unwell, it’s best to visit your GP.


    Find the right home blood test for you
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    Authors and editors

    • Reviewed and updated by

      Dr Bhavini Shah
      GMC number: 7090158
      Date reviewed: 14th March 2024

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