Overview
Vitamins are a group of nutrients your body needs to work properly. They do not provide calories, but they help the body use food, make cells, maintain tissues, and support normal body functions. There are water-soluble vitamins, such as vitamin C and the B vitamins, and fat-soluble vitamins, such as vitamins A, D, E, and K. Because the body stores some vitamins more than others, both deficiency and excess can happen.
Key Symptoms
Vitamin problems do not cause one single set of symptoms. Depending on which vitamin is low or high, symptoms may include tiredness, weakness, mouth sores, skin changes, vision problems, numbness, easy bruising, bone pain, or frequent infections. Some deficiencies develop slowly and may be hard to notice at first. Symptoms can also overlap with many other health conditions.
Causes and Risk Factors
Vitamin deficiency can happen if the diet does not include enough variety, if the body cannot absorb nutrients well, or if a person has higher needs during certain life stages. Risk factors may include restrictive eating patterns, alcohol misuse, certain digestive disorders, some medicines, older age, pregnancy, and limited sun exposure for vitamin D. Vitamin excess is more likely from supplements than from food alone. Taking multiple products with the same ingredients can raise the risk of harmful intake.
Who Is Affected
Anyone can have low or high vitamin levels, but the risk is not the same for everyone. Infants, children, pregnant people, older adults, people with chronic digestive conditions, and people with very limited diets may be more affected. People living in areas with low sunlight or who spend little time outdoors may be more likely to have low vitamin D. Access to varied foods and healthcare also influences risk.
Prevention
For most people, the main way to prevent vitamin problems is to eat a varied diet that includes fruits, vegetables, whole grains, beans, nuts, and other nutrient-rich foods. Follow local public health guidance on fortified foods, infant feeding, and vitamin D where relevant. Avoid taking high-dose supplements unless a healthcare professional recommends them. Keep supplements out of reach of children.
Diagnosis and Tests
Healthcare professionals diagnose vitamin problems by asking about symptoms, diet, medical history, medicines, and sometimes ordering blood tests. Not every vitamin level needs routine testing, and testing depends on the person's symptoms and risk factors. In some cases, signs on physical examination can suggest a deficiency. Results are interpreted together with the whole clinical picture.
Treatment Categories
Treatment depends on whether the problem is too little or too much of a specific vitamin. Approaches may include dietary changes, treating an underlying absorption problem, stopping unnecessary supplements, or using medically guided supplementation. Some deficiencies need closer follow-up because they can affect the blood, nerves, or bones. Treatment should be individualized by a qualified healthcare professional.
Diet and Lifestyle
A practical approach is to build meals around a range of foods rather than focusing on a single nutrient. Different vitamins are found in different foods, so variety matters. If you follow a vegan, vegetarian, highly restricted, or medically necessary diet, ask a healthcare professional whether you should review your nutrient intake. Read supplement labels carefully to avoid doubling up on ingredients.
When to Seek Medical Care
Seek medical care if you have ongoing tiredness, unexplained weakness, numbness, bone pain, repeated mouth sores, major diet restriction, or concerns about a possible deficiency or supplement side effect. Also seek advice if you are pregnant, planning pregnancy, caring for an infant, or have a condition that affects digestion or absorption. A clinician can help decide whether testing or treatment is appropriate.
When It May Be an Emergency
Get urgent medical help if a child may have swallowed vitamins or supplements, especially iron-containing products. Emergency care is also important for severe symptoms such as confusion, trouble breathing, seizures, severe dehydration, or sudden vision changes. These symptoms can have many causes, including possible vitamin-related toxicity or deficiency complications.