14 of the most overlooked signs of a vitamin deficiency

From brittle nails or mouth ulcers to scaly skin or hair loss, the signs of a vitamin deficiency can be varied. Our nutritionist explains how to spot a vitamin deficiency and, most importantly, how to address it with simple food inclusions.

Having low levels of essential micronutrients is more common than you might think, with almost 50% of UK adults struggling to get their vitamin needs from their diet. Inadequate intake can have far-reaching implications, depending on the vitamin concerned and the length of time levels are low. The consequences may include a compromised immune system, reduced energy, nerve damage and cognitive dysfunction. Learn how to identify common deficiency symptoms, why they occur and which foods may fix the problem.

Why are vitamin deficiencies common?

With more than half of the calories we consume in the UK coming from ultra-processed food (UPF), it’s not a huge surprise that our diets are low in these essential micronutrients. UPFs are typically high in saturated fat, salt and sugar, and low in fibre and micronutrients, like vitamins. Add to this the increased use of weight-loss medication and it becomes evident why we may run the risk of deficiency. An estimated 1.5-2 million UK adults are currently using weight-loss jabs, including products such as Wegovy and Ozempic; this medication can cause vitamin deficiencies due to a significant reduction in food intake and delayed stomach emptying. Studies suggest that over 20% of users are likely to experience a vitamin deficiency within the first 12 months of use. The most common deficiencies are for vitamins D, B12, A and C.

Discover our full range of health benefit guides including vitamins – what do I need? and the top 10 sources of vitamin C.

14 symptoms of vitamin deficiency

1. Brittle nails

You may not be familiar with the vitamin biotin (also known as vitamin B7), but it’s key for healthy, strong nails. Biotin helps the body produce keratin, the tough protein that gives nails their strength.

Foods to eat to increase biotin: Eggs, organ meats like liver, salmon, almonds, peanuts, soybeans and lentils.

2. Hair loss

Healthy hair also needs biotin because it’s essential for producing keratin. Keratin in the hair creates strength and elasticity and helps protect the hair shaft from the damage caused by heat treatment, chemicals and environmental pollutants.

Foods to eat to increase biotin: Nutritional yeast, walnuts, sunflower seeds, chicken liver, sardines and mushrooms.

3. Dry/itchy skin

Skin problems can arise from a number of nutrient deficiencies, but low levels of vitamins A and D can lead to dry, itchy or scaly skin as well as a condition called seborrheic dermatitis. We need these vitamins because they regulate cell turnover, reduce inflammation and help maintain a protective skin barrier.

Foods to eat to increase vitamins A and D: Oily fish including sardines and mackerel, eggs, dairy foods and fortified dairy alternatives.

4. Cracked lips

Although not always to blame for the cracks in the corners of your lips, low levels of both vitamins B2 and B6 may be contributing to the problem.

Foods to eat to increase vitamins B2 and B6: Liver, chicken, turkey, tuna, eggs, milk, banana and fortified breakfast cereals.

5. Mouth ulcers

Mouth ulcers are often caused by a deficiency in vitamins B12 and B9 (folate). We need these vitamins for mucosal (lining of the mouth) skin cell production, tissue repair and immune function.

Foods to eat to increase vitamins B12 and B9: Liver, red meat, tuna, trout, shellfish, eggs and dairy products as well as fortified dairy alternatives.

6. Easy bruising

Low levels of vitamins C and K can explain why you bruise easily. We need vitamin C for collagen production; this protein acts like scaffolding to the skin as well as for the walls of our blood vessels. Vitamin K is needed for the blood to clot properly, and low levels may lead to bruising and easy bleeding.

Foods to eat to increase vitamins C and K: Leafy greens like kale, spinach and chard, broccoli and cabbage, as well as kiwi and blackberries.

7. Slow wound healing

Low levels of vitamins C and D are typically responsible for slow wound healing. This is because of vitamin C’s role in collagen formation and tissue repair and vitamin D’s role in immunity and skin health.

Foods to eat to increase vitamins C and D: Peppers, citrus fruit and strawberries (for vitamin C) and oily fish including trout, fortified spreads and yogurts and eggs (for vitamin D).

8. Bleeding gums

Low levels of vitamin C will weaken gum tissue and cause inflammation. Severely low levels will result in scurvy, which has symptoms including bleeding gums, bruising and tooth loss.

Foods to eat to increase vitamin C: Oranges, lemons, blackcurrants, papaya, brussels sprouts.

9. Fatigue

Poor energy levels and fatigue can be caused by low levels of vitamins D, B12 and B9 (folate). Vitamin D can cause muscle weakness and aches, whereas low levels of B12 and folate can cause a type of anaemia-related tiredness.

Foods to eat to increase vitamins D, B12 and B9: Fatty fish are ideal for all three of these vitamins; examples include sardines, salmon and trout. In addition, dairy and fortified dairy-free alternatives as well as fortified cereals

10. Memory loss and cognitive changes

Low levels of vitamins B12, B1 and B6 are all linked to memory loss, cognitive decline and dementia-like symptoms. Deficiency in these vitamins is common especially as we get older, and also potentially for those following a plant-focused diet.

Foods to eat to increase vitamins B12, B1 and B6: Beef, pork, liver, poultry, tuna, cod, shellfish, eggs and dairy foods as well as fortified nutritional yeast and marmite.

11. Difficulty seeing in low light

A deficiency in vitamin A can cause ‘night blindness’, or the inability to see in dim light. We need vitamin A to form rhodopsin, a light-sensitive protein in the retina that allows us to see in low-light conditions.

Foods to eat to increase vitamin A: Orange fruit and vegetables such as carrots, pumpkin and sweet potato, as well as eggs, liver and herring.

12. Joint pain

Low levels of vitamins D, K and B12 are linked to joint pain. The reasons behind this are varied – vitamin B12 affects nerve function and inflammation, whereas low levels of vitamins D and K may be associated with osteoarthritis.

Foods to eat to increase vitamins D, K and B12: Oily fish, including herring and sardines, eggs and fortified food products like spreads and breakfast cereals as well as liver and beef.

13. Muscle cramps

Low levels of vitamins D, B12 and B6 may lead to muscle cramps, spasms and weakness, primarily due to the roles these vitamins have in muscle and nerve function.

Foods to eat to increase vitamins D, B12 and B6: Oily fish, beef, liver, eggs, milk and yogurt and fortified foods products like breakfast cereals.

14. Tongue changes

A swollen tongue or a burning or tingling sensation on the tongue may be caused by vitamin B deficiencies, particularly B12, B9 (folate), B3 and B2.

Foods to eat to increase vitamins B12, B9, B3 and B2: Salmon, beef, liver, eggs, leafy greens and legumes including lentils and peas, as well as fortified nutritional yeast and breakfast cereals.

What is the most common vitamin deficiency?

In the UK, vitamin D is the most common vitamin deficiency, with low levels reported to affect about 50% of the population. Diet is not the only explanation, because the body can make vitamin D through the action of sunlight on the skin. However, due to the UK’s northern location, the sun’s rays are not strong enough between October and early March, which is why the UK government suggests we all consider a vitamin D supplement. Dietary sources of vitamin D are limited, with the best sources being oily fish, egg yolks and dairy foods or fortified dairy alternatives.

How do I know what vitamins I’m lacking?

Your doctor will be able to assess your symptoms, diet and risk factors and complete a physical examination looking for signs such as skin issues, brittle nails, hair loss or tongue changes. Based on this review, your GP may suggest a blood test to check vitamin levels. This is the most effective way to measure nutrient levels and determine whether you have a deficiency.

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Kerry Torrens BSc. (Hons) PgCert MBANT is a BANT Registered Nutritionist® with a postgraduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including Good Food.

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