Vitamin D

Overview

Vitamin D is a nutrient your body needs to stay healthy. It helps your body absorb calcium, which is important for strong bones and teeth. It also helps your muscles, heart, lungs, and brain work well. Your body makes vitamin D when your skin is exposed to sunlight, and you can also get it from some foods and supplements.

Yes, low vitamin D is very common. Many people around the world have low levels, especially during winter months or if they spend little time outdoors.

Vitamin D deficiency can affect anyone, but it is more likely in people who have darker skin, are older, live in places with little sunshine, stay indoors a lot, or have conditions that make it hard to absorb nutrients.

Symptoms

Common symptoms

• Feeling tired or weak
• Bone pain or aches
• Muscle weakness or cramps
• Low mood or depression

Symptoms in children

• Delayed growth or short height
• Bowed legs or knocked knees
• Soft or weak bones, which can lead to rickets
• Irritability or being fussy

Symptoms in older adults

• Increased risk of falls and fractures
• Bone pain, especially in the lower back or legs
• Muscle weakness, which can affect balance and mobility
• Difficulty doing everyday activities

Causes

Main causes

• Not getting enough sunlight on your skin
• A diet that is low in vitamin D-rich foods
• Your body not being able to absorb vitamin D properly due to certain health conditions
• Having darker skin, which makes it harder for your body to make vitamin D from sunlight

Risk factors

• Living far from the equator or in places with long winters
• Staying indoors most of the time or covering your skin for cultural or religious reasons
• Being older, because the skin makes vitamin D less effectively with age
• Having a body mass index (BMI) in the obesity range
• Having a digestive condition like Crohn's disease or celiac disease
• Taking certain medicines that affect vitamin D levels

When to see a doctor

See a doctor urgently if:

• If you have severe bone pain or muscle weakness that interferes with daily life, see a doctor within a day or two.

Book a routine appointment if:

• If you have risk factors for low vitamin D, such as being older or having a condition that affects absorption, ask your doctor about a blood test.
• If you feel tired, achy, or low in mood for no clear reason, it is reasonable to bring up vitamin D with your doctor.

Diagnosis

Doctors diagnose vitamin D deficiency with a simple blood test. The test measures the level of vitamin D in your blood. Your doctor will compare the results to a normal range and decide if you need treatment.

Tests that may be done

• Blood test for 25-hydroxyvitamin D, which is the main form of vitamin D in your blood
• Sometimes a calcium level test, because vitamin D and calcium work closely together

What to expect at your appointment

A healthcare professional will take a small sample of blood from your arm. It takes only a few minutes and feels like a quick pinch. You should get your results within a few days, and your doctor will explain what they mean.

Treatment

Treatment usually involves raising your vitamin D levels safely. This can be done with more sunlight, vitamin D-rich foods, and supplements. Your doctor will give you advice based on your blood test results and your overall health.

Self-care at home

• Spend short periods of time in sunlight without sunscreen on your arms and legs, but be careful not to burn. The amount of time varies depending on your skin type, where you live, and the season.
• Eat foods that naturally contain vitamin D, such as oily fish (like salmon or sardines), egg yolks, and fortified foods like some breakfast cereals and dairy products.
• Follow your doctor's advice about supplements — do not take more than recommended.

Medical treatments

If your vitamin D level is very low, your doctor may recommend a high-dose supplement for a few weeks or months, and then a lower maintenance dose. In some cases, an underlying health condition that affects vitamin D absorption needs to be treated. Always take supplements exactly as your doctor or pharmacist advises.

Living with this condition

If you have low vitamin D, the main thing is to build new habits. Try to get a little sun every day, include vitamin D-rich foods in your meals, and take supplements if your doctor recommended them. It may take a few months of treatment before you feel a difference, so be patient.

Lifestyle tips

• Get outside for at least 10 to 20 minutes of sunshine a few times a week, if possible.
• Keep moving with gentle exercises like walking, stretching, or dancing to support bone and muscle strength.
• Be consistent with any prescribed supplements — set a daily reminder if needed.

Diet and exercise

A balanced diet supports your bones and muscles. Include foods rich in vitamin D and calcium, such as dairy products, leafy greens, and fish. Regular weight-bearing exercise, like walking or climbing stairs, helps your body use vitamin D to build strong bones.

Mental health and emotional wellbeing

Low vitamin D has been linked to low mood and depression in some people. Treating a deficiency may help improve your mood, but if you feel persistently sad or anxious, talk to a healthcare provider.

Prevention

Vitamin D deficiency can often be prevented with regular, sensible sun exposure and a diet rich in vitamin D. If you are at high risk, your doctor may recommend a daily supplement to keep your levels healthy.

Screening programmes

Routine screening is not recommended for everyone, but your doctor may check your vitamin D level if you have risk factors or symptoms of deficiency.

Complications

If left untreated

• In children, severe deficiency can lead to rickets, which causes soft and deformed bones.
• In adults, low vitamin D can cause osteomalacia, a condition where bones become soft and painful.
• Long-term low vitamin D increases the risk of osteoporosis, falls, and bone fractures, especially in older adults.

Long-term outlook

The outlook for vitamin D deficiency is very good. Once your levels are back to normal with treatment, most symptoms improve, and the risk of long-term bone problems decreases. With the right support, you can keep your vitamin D levels healthy.

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