Vitamin D
Vitamin D
Vitamin D is essential for calcium absorption and bone health. Made in the body through sunlight absorption but also found in eggs yolks and dairy products.
Vitamin D is essential for calcium absorption and bone health. Made in the body through sunlight absorption but also found in eggs yolks and dairy products.
Vitamin D
Normal range
Normal range
51-75 nmol/L
51-75 nmol/L
Normal range
51-75 nmol/L
51-75 nmol/L
Normal range
Vitamin D
Vitamin D
Vitamin D is essential for calcium absorption and bone health. Made in the body through sunlight absorption but also found in eggs yolks and dairy products.
Vitamin D
Normal range
51-75 nmol/L
Normal range
51-75 nmol/L
51-75 nmol/L
Normal range
Vitamin D
Vitamin D
Vitamin D is essential for calcium absorption and bone health. Made in the body through sunlight absorption but also found in eggs yolks and dairy products.
Vitamin D
Normal range
51-75 nmol/L
Normal range
51-75 nmol/L
51-75 nmol/L
Normal range
Vitamin D
Dr. Shad Asinger
MBBS GPST
The Sunshine Vitamin
The Sunshine Vitamin
Vitamin D does more than help you absorb calcium; it’s your body’s natural immunity booster, bone protector, and even mood stabiliser. Often called the “sunshine vitamin” because your skin makes it when exposed to sunlight, vitamin D acts more like a hormone than a vitamin, influencing everything from inflammation to brain health. When your levels drop, your body might whisper- fatigue, low mood, frequent illness- or shout, in the form of weakened bones, muscle aches, or long-term disease risk.
Vitamin D does more than help you absorb calcium; it’s your body’s natural immunity booster, bone protector, and even mood stabiliser. Often called the “sunshine vitamin” because your skin makes it when exposed to sunlight, vitamin D acts more like a hormone than a vitamin, influencing everything from inflammation to brain health. When your levels drop, your body might whisper- fatigue, low mood, frequent illness- or shout, in the form of weakened bones, muscle aches, or long-term disease risk.
When Vitamin D Levels Are Too Low
When Vitamin D Levels Are Too Low
When Vitamin D Levels Are Too Low
Explore how low vitamin D can affect your bones, immunity, energy, and mental health—often without you realising.
Read more
Why Vitamin D Is So Essential
Why Vitamin D Is So Essential
Why Vitamin D Is So Essential
Learn how this hormone-like vitamin supports skeletal strength, immune defence, and emotional wellbeing.
Read more
What Causes Deficiency in the Sunshine Vitamin?
What Causes Deficiency in the Sunshine Vitamin?
What Causes Deficiency in the Sunshine Vitamin?
Understand why even sunny countries aren’t immune to low vitamin D—and who’s most at risk.`
Read more
Understanding Your Results
Understanding Your Results
Understanding Your Results
Break down what your vitamin D numbers really mean, and when to consider supplements or lifestyle changes.
Read more
When Vitamin D Levels Are Too Low
Low vitamin D is like building a house without a foundation - your bones, immune system, and energy levels can’t fully support you. Early signs of deficiency are subtle and often misattributed: tiredness, low mood, frequent infections, muscle aches, or poor recovery after activity. For many, it feels like “just being run down”...but there’s a reason.
More severe deficiency can lead to:
Bone pain or fractures: Vitamin D is essential for calcium absorption. Low levels lead to osteomalacia (soft bones) in adults and rickets in children.
Muscle weakness: Especially in the legs, increasing the risk of falls and poor physical performance.
Low mood and depression: Vitamin D plays a role in brain function and serotonin regulation.
Weakened immunity: You may find yourself catching colds, flu, or infections more often.
Even mild deficiency, when prolonged, has been linked to increased risk of osteoporosis, autoimmune diseases, cardiovascular disease, and even some cancers.
When Vitamin D Levels Are Too Low
Low vitamin D is like building a house without a foundation - your bones, immune system, and energy levels can’t fully support you. Early signs of deficiency are subtle and often misattributed: tiredness, low mood, frequent infections, muscle aches, or poor recovery after activity. For many, it feels like “just being run down”...but there’s a reason.
More severe deficiency can lead to:
Bone pain or fractures: Vitamin D is essential for calcium absorption. Low levels lead to osteomalacia (soft bones) in adults and rickets in children.
Muscle weakness: Especially in the legs, increasing the risk of falls and poor physical performance.
Low mood and depression: Vitamin D plays a role in brain function and serotonin regulation.
Weakened immunity: You may find yourself catching colds, flu, or infections more often.
Even mild deficiency, when prolonged, has been linked to increased risk of osteoporosis, autoimmune diseases, cardiovascular disease, and even some cancers.
When Vitamin D Levels Are Too Low
Low vitamin D is like building a house without a foundation - your bones, immune system, and energy levels can’t fully support you. Early signs of deficiency are subtle and often misattributed: tiredness, low mood, frequent infections, muscle aches, or poor recovery after activity. For many, it feels like “just being run down”...but there’s a reason.
More severe deficiency can lead to:
Bone pain or fractures: Vitamin D is essential for calcium absorption. Low levels lead to osteomalacia (soft bones) in adults and rickets in children.
Muscle weakness: Especially in the legs, increasing the risk of falls and poor physical performance.
Low mood and depression: Vitamin D plays a role in brain function and serotonin regulation.
Weakened immunity: You may find yourself catching colds, flu, or infections more often.
Even mild deficiency, when prolonged, has been linked to increased risk of osteoporosis, autoimmune diseases, cardiovascular disease, and even some cancers.
Why Vitamin D Is So Essential
Vitamin D is fat-soluble and behaves more like a hormone than a typical vitamin. It binds to receptors in nearly every cell in your body. Its key roles include:
Bone Health: Vitamin D stimulates the production of a protein in your gut called calbindin, which helps absorb calcium and phosphorus into the bloodstream. Without enough vitamin D, your body absorbs less than half the calcium from food—even if your intake is high. This can lead to weakened bones, softening conditions like osteomalacia in adults or ricketsin children.
Immune Regulation: Vitamin D supports both innate immunity (your first-line defence) and adaptive immunity (targeted responses). It enhances the activity of antimicrobial peptides in immune cells and helps balance inflammatory signals—reducing overreactions that can worsen infections or autoimmune conditions. It’s particularly linked to protection against respiratory infections like colds, flu, and even COVID-19.
Mood and Brain Function: Vitamin D receptors are found throughout the brain. It helps regulate neurotransmitters such as serotonin and dopamine, which are essential for mood stability, motivation, and mental clarity. Low levels of vitamin D are consistently associated with depression, cognitive decline, and even an increased risk of dementia.
Muscle Function: Vitamin D plays a direct role in muscle contraction and repair by regulating calcium transport in muscle fibres. It helps maintain muscle strength and coordination, especially in the legs—reducing the risk of falls and fractures, particularly in older adults.
Chronic Disease Prevention: Vitamin D has anti-inflammatory and immune-modulating effects that are thought to contribute to a lower risk of chronic diseases. Research links adequate levels with reduced risks of:
Cardiovascular disease (through effects on blood pressure and vessel health)
Type 2 diabetes (via improved insulin sensitivity)
Autoimmune diseases like multiple sclerosis
Certain cancers, especially colorectal and breast, though evidence is still evolving
Given how many systems it affects, even a small dip in vitamin D can ripple throughout your body.
Why Vitamin D Is So Essential
Vitamin D is fat-soluble and behaves more like a hormone than a typical vitamin. It binds to receptors in nearly every cell in your body. Its key roles include:
Bone Health: Vitamin D stimulates the production of a protein in your gut called calbindin, which helps absorb calcium and phosphorus into the bloodstream. Without enough vitamin D, your body absorbs less than half the calcium from food—even if your intake is high. This can lead to weakened bones, softening conditions like osteomalacia in adults or ricketsin children.
Immune Regulation: Vitamin D supports both innate immunity (your first-line defence) and adaptive immunity (targeted responses). It enhances the activity of antimicrobial peptides in immune cells and helps balance inflammatory signals—reducing overreactions that can worsen infections or autoimmune conditions. It’s particularly linked to protection against respiratory infections like colds, flu, and even COVID-19.
Mood and Brain Function: Vitamin D receptors are found throughout the brain. It helps regulate neurotransmitters such as serotonin and dopamine, which are essential for mood stability, motivation, and mental clarity. Low levels of vitamin D are consistently associated with depression, cognitive decline, and even an increased risk of dementia.
Muscle Function: Vitamin D plays a direct role in muscle contraction and repair by regulating calcium transport in muscle fibres. It helps maintain muscle strength and coordination, especially in the legs—reducing the risk of falls and fractures, particularly in older adults.
Chronic Disease Prevention: Vitamin D has anti-inflammatory and immune-modulating effects that are thought to contribute to a lower risk of chronic diseases. Research links adequate levels with reduced risks of:
Cardiovascular disease (through effects on blood pressure and vessel health)
Type 2 diabetes (via improved insulin sensitivity)
Autoimmune diseases like multiple sclerosis
Certain cancers, especially colorectal and breast, though evidence is still evolving
Given how many systems it affects, even a small dip in vitamin D can ripple throughout your body.
Why Vitamin D Is So Essential
Vitamin D is fat-soluble and behaves more like a hormone than a typical vitamin. It binds to receptors in nearly every cell in your body. Its key roles include:
Bone Health: Vitamin D stimulates the production of a protein in your gut called calbindin, which helps absorb calcium and phosphorus into the bloodstream. Without enough vitamin D, your body absorbs less than half the calcium from food—even if your intake is high. This can lead to weakened bones, softening conditions like osteomalacia in adults or ricketsin children.
Immune Regulation: Vitamin D supports both innate immunity (your first-line defence) and adaptive immunity (targeted responses). It enhances the activity of antimicrobial peptides in immune cells and helps balance inflammatory signals—reducing overreactions that can worsen infections or autoimmune conditions. It’s particularly linked to protection against respiratory infections like colds, flu, and even COVID-19.
Mood and Brain Function: Vitamin D receptors are found throughout the brain. It helps regulate neurotransmitters such as serotonin and dopamine, which are essential for mood stability, motivation, and mental clarity. Low levels of vitamin D are consistently associated with depression, cognitive decline, and even an increased risk of dementia.
Muscle Function: Vitamin D plays a direct role in muscle contraction and repair by regulating calcium transport in muscle fibres. It helps maintain muscle strength and coordination, especially in the legs—reducing the risk of falls and fractures, particularly in older adults.
Chronic Disease Prevention: Vitamin D has anti-inflammatory and immune-modulating effects that are thought to contribute to a lower risk of chronic diseases. Research links adequate levels with reduced risks of:
Cardiovascular disease (through effects on blood pressure and vessel health)
Type 2 diabetes (via improved insulin sensitivity)
Autoimmune diseases like multiple sclerosis
Certain cancers, especially colorectal and breast, though evidence is still evolving
Given how many systems it affects, even a small dip in vitamin D can ripple throughout your body.
What Causes Deficiency in the Sunshine Vitamin?
You’d think living in a sunny country would protect against deficiency - but vitamin D deficiency is still widespread, especially in the UK. Here’s why:
Lack of sun exposure: In the UK, sunlight is too weak for vitamin D production from October to March. Cloudy days, sunscreen use, and staying indoors also block production.
Darker skin: Higher melanin levels reduce the skin’s ability to produce vitamin D from sunlight, putting Black and South Asian individuals at higher risk.
Ageing: Older adults produce less vitamin D in response to sun and absorb less from food.
Obesity: Vitamin D is stored in fat tissue, which can sequester it and reduce its availability.
Low dietary intake: Few foods naturally contain vitamin D - fatty fish, egg yolks, and fortified foods are the main sources.
Digestive or kidney issues: Conditions like coeliac disease, Crohn’s, or chronic kidney disease affect absorption or conversion to active vitamin D.
Even healthy people can be deficient, especially in winter, which is why routine testing is becoming more common.
What Causes Deficiency in the Sunshine Vitamin?
You’d think living in a sunny country would protect against deficiency - but vitamin D deficiency is still widespread, especially in the UK. Here’s why:
Lack of sun exposure: In the UK, sunlight is too weak for vitamin D production from October to March. Cloudy days, sunscreen use, and staying indoors also block production.
Darker skin: Higher melanin levels reduce the skin’s ability to produce vitamin D from sunlight, putting Black and South Asian individuals at higher risk.
Ageing: Older adults produce less vitamin D in response to sun and absorb less from food.
Obesity: Vitamin D is stored in fat tissue, which can sequester it and reduce its availability.
Low dietary intake: Few foods naturally contain vitamin D - fatty fish, egg yolks, and fortified foods are the main sources.
Digestive or kidney issues: Conditions like coeliac disease, Crohn’s, or chronic kidney disease affect absorption or conversion to active vitamin D.
Even healthy people can be deficient, especially in winter, which is why routine testing is becoming more common.
What Causes Deficiency in the Sunshine Vitamin?
You’d think living in a sunny country would protect against deficiency - but vitamin D deficiency is still widespread, especially in the UK. Here’s why:
Lack of sun exposure: In the UK, sunlight is too weak for vitamin D production from October to March. Cloudy days, sunscreen use, and staying indoors also block production.
Darker skin: Higher melanin levels reduce the skin’s ability to produce vitamin D from sunlight, putting Black and South Asian individuals at higher risk.
Ageing: Older adults produce less vitamin D in response to sun and absorb less from food.
Obesity: Vitamin D is stored in fat tissue, which can sequester it and reduce its availability.
Low dietary intake: Few foods naturally contain vitamin D - fatty fish, egg yolks, and fortified foods are the main sources.
Digestive or kidney issues: Conditions like coeliac disease, Crohn’s, or chronic kidney disease affect absorption or conversion to active vitamin D.
Even healthy people can be deficient, especially in winter, which is why routine testing is becoming more common.
Understanding Your Results
Vitamin D is measured in the blood as 25-hydroxyvitamin D (25(OH)D) and reported in nmol/L in the UK. Here’s how to interpret your results:
Deficient: <25 nmol/L
Insufficient: 25–50 nmol/L
Normal: 51–75 nmol/L
Optimal: 76–175 nmol/L
High (but still within normal range): 176–200 nmol/L
Excess: 201–375 nmol/L
Toxic: >375 nmol/L
Low levels (<50 nmol/L) may lead to symptoms like fatigue, bone pain, muscle weakness, and increased susceptibility to infections. Levels in the optimal range (76–175 nmol/L) are considered ideal for maintaining bone health, supporting immune function, and reducing chronic disease risk.
If your vitamin D is low, your GP may recommend:
Supplementation: Typically 800–2000 IU daily. Short-term high doses (up to 4000 IU) may be prescribed under medical supervision in severe deficiency.
Lifestyle support: Get 10–20 minutes of direct sun exposure daily (spring/summer, arms and legs), and include foods like oily fish, eggs, and fortified dairy or cereals.
Re-testing: Check levels again after 8–12 weeks to confirm improvement.
Note: Vitamin D toxicity is rare but can occur with long-term excessive supplementation. Levels above 375 nmol/L are considered potentially toxic and may cause calcium imbalances, kidney damage, or other complications—so always follow clinical advice when supplementing.
Understanding Your Results
Vitamin D is measured in the blood as 25-hydroxyvitamin D (25(OH)D) and reported in nmol/L in the UK. Here’s how to interpret your results:
Deficient: <25 nmol/L
Insufficient: 25–50 nmol/L
Normal: 51–75 nmol/L
Optimal: 76–175 nmol/L
High (but still within normal range): 176–200 nmol/L
Excess: 201–375 nmol/L
Toxic: >375 nmol/L
Low levels (<50 nmol/L) may lead to symptoms like fatigue, bone pain, muscle weakness, and increased susceptibility to infections. Levels in the optimal range (76–175 nmol/L) are considered ideal for maintaining bone health, supporting immune function, and reducing chronic disease risk.
If your vitamin D is low, your GP may recommend:
Supplementation: Typically 800–2000 IU daily. Short-term high doses (up to 4000 IU) may be prescribed under medical supervision in severe deficiency.
Lifestyle support: Get 10–20 minutes of direct sun exposure daily (spring/summer, arms and legs), and include foods like oily fish, eggs, and fortified dairy or cereals.
Re-testing: Check levels again after 8–12 weeks to confirm improvement.
Note: Vitamin D toxicity is rare but can occur with long-term excessive supplementation. Levels above 375 nmol/L are considered potentially toxic and may cause calcium imbalances, kidney damage, or other complications—so always follow clinical advice when supplementing.
Understanding Your Results
Vitamin D is measured in the blood as 25-hydroxyvitamin D (25(OH)D) and reported in nmol/L in the UK. Here’s how to interpret your results:
Deficient: <25 nmol/L
Insufficient: 25–50 nmol/L
Normal: 51–75 nmol/L
Optimal: 76–175 nmol/L
High (but still within normal range): 176–200 nmol/L
Excess: 201–375 nmol/L
Toxic: >375 nmol/L
Low levels (<50 nmol/L) may lead to symptoms like fatigue, bone pain, muscle weakness, and increased susceptibility to infections. Levels in the optimal range (76–175 nmol/L) are considered ideal for maintaining bone health, supporting immune function, and reducing chronic disease risk.
If your vitamin D is low, your GP may recommend:
Supplementation: Typically 800–2000 IU daily. Short-term high doses (up to 4000 IU) may be prescribed under medical supervision in severe deficiency.
Lifestyle support: Get 10–20 minutes of direct sun exposure daily (spring/summer, arms and legs), and include foods like oily fish, eggs, and fortified dairy or cereals.
Re-testing: Check levels again after 8–12 weeks to confirm improvement.
Note: Vitamin D toxicity is rare but can occur with long-term excessive supplementation. Levels above 375 nmol/L are considered potentially toxic and may cause calcium imbalances, kidney damage, or other complications—so always follow clinical advice when supplementing.
The Takeaway
Vitamin D is your body’s multitasking protector - supporting bones, immunity, muscles, and mood. But because it’s hard to get from diet and sunlight alone, deficiency is incredibly common, especially in winter or among high-risk groups. If you’re feeling tired, achy, low in mood, or constantly catching bugs, your vitamin D levels may be quietly holding you back. A simple blood test can reveal if you need support—and with the right supplementation and habits, you can rebuild your reserves and restore your vitality.
The Takeaway
Vitamin D is your body’s multitasking protector - supporting bones, immunity, muscles, and mood. But because it’s hard to get from diet and sunlight alone, deficiency is incredibly common, especially in winter or among high-risk groups. If you’re feeling tired, achy, low in mood, or constantly catching bugs, your vitamin D levels may be quietly holding you back. A simple blood test can reveal if you need support—and with the right supplementation and habits, you can rebuild your reserves and restore your vitality.
The Takeaway
Vitamin D is your body’s multitasking protector - supporting bones, immunity, muscles, and mood. But because it’s hard to get from diet and sunlight alone, deficiency is incredibly common, especially in winter or among high-risk groups. If you’re feeling tired, achy, low in mood, or constantly catching bugs, your vitamin D levels may be quietly holding you back. A simple blood test can reveal if you need support—and with the right supplementation and habits, you can rebuild your reserves and restore your vitality.
References
National Institute for Health and Care Excellence (NICE). Vitamin D: supplement use in specific population groups. 2022.
NHS. Vitamin D. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
Scientific Advisory Committee on Nutrition (SACN). Vitamin D and Health. Public Health England, 2016.
British Medical Journal. Vitamin D: Effects on skeletal and extra-skeletal health. BMJ 2020;369:m249
References
National Institute for Health and Care Excellence (NICE). Vitamin D: supplement use in specific population groups. 2022.
NHS. Vitamin D. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
Scientific Advisory Committee on Nutrition (SACN). Vitamin D and Health. Public Health England, 2016.
British Medical Journal. Vitamin D: Effects on skeletal and extra-skeletal health. BMJ 2020;369:m249
References
National Institute for Health and Care Excellence (NICE). Vitamin D: supplement use in specific population groups. 2022.
NHS. Vitamin D. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
Scientific Advisory Committee on Nutrition (SACN). Vitamin D and Health. Public Health England, 2016.
British Medical Journal. Vitamin D: Effects on skeletal and extra-skeletal health. BMJ 2020;369:m249
Research articles
Research articles
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