Vitamin D Deficiency: 5 Main Symptoms and How to Treat It

Vitamin D is vital for maintaining bone health, regulating the immune system and ensuring the body functions properly. It is obtained chiefly through sun exposure, although it can also be sourced from foods such as oily fish, eggs and fortified dairy products, as well as supplements. A lack of this nutrient can trigger a range of symptoms that affect both physical and mental wellbeing.

“Subclinical vitamin D deficiency, identified by a low serum concentration of 25 OH Vitamin D, is very common today because of reduced sun exposure and the use of sun cream. What many people do not realise is that the well-known ‘sunshine vitamin’ is, conceptually, a hormone, because the body can synthesise it entirely and because it has specific receptors in several body tissues,” says endocrinologist Thaís Vital.

Below are the main symptoms of vitamin D deficiency.

1. Persistent fatigue

Ongoing tiredness is among the earliest signs of vitamin D deficiency. Insufficient levels of this nutrient can interfere with energy production in the body, causing fatigue even after a good rest. This is because vitamin D plays an essential role in cellular metabolism, and its absence may reduce the energy supply available to cells.

2. Muscle pain and weakness

Vitamin D is essential for muscle function, and a deficiency may lead to muscle aches and weakness. This is because it contributes to calcium absorption, a mineral needed for proper muscle contraction. As a result, people with low levels of this nutrient may experience widespread muscle pain and even struggle with everyday tasks, such as climbing stairs or lifting objects.

3. Bone pain

Bone health relies directly on vitamin D, which helps the body absorb calcium and phosphorus, both of which are essential for keeping bones strong. “Its effect on bone metabolism is to increase duodenal calcium absorption and act directly on bone, taking part in the mineralisation process […]”, explains Thaís Vital.

Consequently, a deficiency of this nutrient can cause bone pain, particularly in the lower back and legs. If it persists for a prolonged period, it may even result in osteomalacia, a condition that weakens and softens the bones.

4. Reduced immunity

This nutrient has an important role in modulating the immune system, helping the body fight infections. Therefore, when vitamin D deficiency is present, the immune system may be impaired, making a person more susceptible to colds, flu and other infections.

According to pharmacist Paula Molari Abdo, the immune system consists of a range of cells that support the body’s defences, protecting it against illnesses and infections caused by external agents such as bacteria, viruses and parasites. When immunity is low, the body finds it harder to protect itself, leaving it more exposed to so-called opportunistic diseases.

5. Depression and mood changes

A lack of vitamin D can also affect mental health. Low levels of this nutrient are associated with increased depressive symptoms because it influences the production of serotonin, a neurotransmitter that regulates mood. People with vitamin D deficiency may experience feelings of sadness, anxiety and irritability.

How to identify and treat vitamin D deficiency

Vitamin D deficiency can be diagnosed through blood tests that measure the nutrient’s levels in the body. If you experience any of the symptoms described, it is important to seek medical advice to confirm whether your levels are low and discuss treatment options.

Getting at least 15 minutes of sun exposure each day is one of the simplest ways to obtain the vitamin, but in many cases, supplementation and dietary adjustments are needed. “Only 20% of our [vitamin D] requirements come from diet. The other 80% is synthesised by the skin through sun exposure,” explains Paula Molari Abdo.

However, it is important to avoid self-medication. “It is worth stressing that vitamin D supplementation beyond daily requirements is not recommended for preventing disease or even improving quality of life. Therefore, consult a doctor to assess whether you genuinely need the supplement and what dose will meet your needs,” concludes the pharmacist.