Are you getting enough vitamins from your daily diet? For many people, the answer may not always be obvious. Vitamin deficiencies can develop gradually, and early symptoms such as tiredness, weakness, poor concentration, numbness or changes in the skin and hair can easily be overlooked.

Vitamins are essential nutrients that support growth, metabolism, immunity, blood formation, nerve function and many other processes. The body needs 13 recognised essential vitamins, most of which must be obtained through food because it cannot produce enough of them on its own.

Vitamin A deficiency commonly affects the eyes. Early signs may include difficulty seeing in dim light, dry eyes and, in more severe cases, Bitot’s spots. Prolonged deficiency can damage vision and weaken the body’s ability to fight infections.

The B-group vitamins play important roles in energy production, blood formation and the nervous system. Thiamine, or vitamin B1, deficiency can cause fatigue, loss of appetite, muscle weakness, confusion and numbness or tingling in the hands and feet.

Riboflavin, or vitamin B2, deficiency may cause cracks at the corners of the mouth, sore throat, swollen lips and skin problems.

Severe niacin, or vitamin B3, deficiency can cause pellagra, which may present with rough or sun-sensitive skin, diarrhoea and neurological symptoms. Pantothenic acid, or vitamin B5, deficiency is rare but may cause extreme tiredness, disturbed sleep, stomach discomfort and burning or numbness in the hands and feet.

Vitamin B6 deficiency can lead to anaemia, skin rashes, cracks around the mouth, a swollen tongue and weakened immunity. Biotin, or vitamin B7, deficiency is uncommon but may cause thinning hair, brittle nails, skin rashes and neurological symptoms.

Folate, or vitamin B9, deficiency may cause megaloblastic anaemia, weakness, fatigue, poor concentration and mouth sores. Vitamin B12 deficiency can also cause anaemia and fatigue, but if left untreated it may affect the nervous system, resulting in numbness, tingling, difficulty walking and problems with balance.

Vitamin C deficiency can lead to scurvy when severe. Warning signs include tiredness, swollen or bleeding gums, easy bruising and slow healing of wounds.

Vitamin D deficiency is another important concern. Vitamin D is essential for healthy bones and muscles. Deficiency may cause bone pain, muscle weakness and weak bones. In children, severe deficiency can cause rickets, while adults may develop osteomalacia.

People who receive little sunlight or have conditions that interfere with nutrient absorption may be particularly vulnerable.

Vitamin E deficiency is uncommon in healthy people but may occur in those with disorders affecting the absorption of fat. Severe deficiency can cause muscle weakness, numbness, loss of sensation and poor coordination.

Vitamin K is important for normal blood clotting, and severe deficiency may cause easy bruising or excessive bleeding.

A varied and balanced diet is the best starting point for preventing deficiencies. Regular consumption of vegetables, fruits, whole grains, beans, nuts, seeds, eggs, milk and dairy products, as well as appropriate sources of fish and meat, can help provide the vitamins the body requires. Sensible exposure to sunlight also helps the body produce vitamin D.

However, symptoms such as fatigue, hair loss, weakness or numbness do not automatically mean someone has a vitamin deficiency. They can be caused by many other conditions. Some people are more vulnerable because of restrictive diets, pregnancy, ageing, digestive disorders or long-term use of medicines.

Anyone experiencing persistent symptoms should seek medical advice rather than relying on self-diagnosis or taking supplements unnecessarily. Blood tests can help establish whether a deficiency exists and determine its severity. Where an underlying illness is responsible, treating that condition is equally important.

Knowing the common signs of vitamin deficiencies can help people pay closer attention to their nutrition and seek appropriate care before complications develop.

The writer is a specialist in internal medicine.