Vitamin D Deficiency

What is Vitamin D Deficiency?

A lack of vitamin D, which is needed for calcium absorption and bone health.

Vitamin D deficiency means that your body is not getting enough vitamin D to stay healthy. Vitamin D helps your body absorb calcium. Calcium is one of the main building blocks of bone. Vitamin D also has a role in your nervous, muscle, and immune systems. You can get vitamin D in three ways: through your skin, from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. But too much sun exposure can lead to skin aging and skin cancer, so many people try to get their vitamin D from other sources. The amount of vitamin D you need each day depends on your age.

Tests often checked alongside this

• Calcium
• Parathyroid hormone (PTH)
• Phosphorus
• Bone density (if deficiency is longstanding)

How this can show up in how you look and feel

• Often no obvious outward signs, especially early on
• Bone or muscle aches
• Fatigue or muscle weakness
• Severe, prolonged deficiency can contribute to bone softening or fractures

What can affect this marker

• Sun exposure and skin tone
• Diet and supplement use
• Body weight and absorption
• Geography and season

What to track over time

• Levels across repeat blood tests
• Response to supplementation
• Bone and muscle symptoms
• Alongside calcium and PTH levels

What to ask your doctor

• What dose of vitamin D do I need?
• How long until levels improve?
• Should I retest after supplementing?
• Could this affect my bones?

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