How Does Vitamin D Deficiency Happen?

And What to Do About It

Feeling tired, achy, or generally low in mood or energy? You might be experiencing the effects of a vitamin D deficiency.

Vitamin D is essential for bones, immunity, and energy, but many people don’t realise when their body is running low or how deficiency develops. This blog aims to explain what vitamin D does for the body, why vitamin D is essential, where it’s stored, and why testing is important to determine if levels are low. If you’ve been wondering how to check your vitamin D levels at home, we explain how the Smith Biomed Vitamin D Test Kit can give answers.

What Vitamin D Does for the Body

And Where It’s Stored

Vitamin D is often referred to as the “sunshine vitamin,” but it’s actually a hormone precursor that supports nearly every system in the body. It:

Strengthens bones by helping absorb calcium and phosphorus
Boosts immune defences and lowers infection risk
Regulates mood and reduces fatigue
Supports muscle and cardiovascular health

Storage: Vitamin D is primarily stored in the liver and fat tissue, where it’s released as needed by the body.

This is why vitamin D is essential; without enough, your body struggles to maintain balance and long-term health.

How Vitamin D Deficiency Develops

Limited Sun Exposure: Sunlight (UVB rays) is the primary source of vitamin D. In many regions in New Zealand, during winter, sunlight exposure can be limited.
Dietary Gaps: Few foods naturally contain vitamin D. Fatty fish, egg yolks, and fortified items help, but often don’t suffice alone.
Absorption Issues & Health Conditions: Conditions such as Crohn’s disease, celiac disease, liver or kidney problems can impede vitamin absorption or activation.
Medications: Certain medications (like steroids or anti-seizure drugs) interfere with vitamin D metabolism.
Age & Skin Pigmentation: As we age, the skin naturally becomes less efficient at producing vitamin D. People with higher levels of melanin in their skin also require more sun exposure to make the same amount of vitamin D.

New Zealand Snapshot: Around 5% of adults in the 2008/09 New Zealand Adult Nutrition Survey were vitamin D deficient, and another 27% were below recommended levels (Ministry of Health, 2012)

Signs of Vitamin D Deficiency

You may not always notice a deficiency straight away, but common signs could include:

Persistent fatigue or low energy
Muscle weakness, aches, or cramps
Frequent colds or infections
Bone or back pain
Brain fog or low mood

Because these symptoms overlap with those of many other conditions, a vitamin D test is essential to confirm if your levels are low. If you want to check your vitamin D levels at home, a quick and convenient option is the Smith Biomed at-home Vitamin D Test Kit, available at your local pharmacy.

Want more on this topic? Our blog Low Vitamin D – Busting Myths breaks down the most common misconceptions and what you really need to know.

What to Do About Low Vitamin D

1. Get Safe Sun Exposure
Aim for short, regular bursts of midday sun (5–20 minutes depending on the skin’s melanin levels) during spring and summer.

2. Eat Vitamin D-Rich Foods
Include oily fish, eggs, fortified dairy products, or plant-based alternatives in your diet.

3. Test Your Levels
The only way to confirm a deficiency is through a vitamin D test. Check your levels using the Smith Biomed at-home Vitamin D Test Kit, available at your local pharmacy.

4. Choose the Right Supplement
If you’re deficient, supplements can help, but the type matters:

Vitamin D3 (cholecalciferol): The most effective form, typically sourced from animal products.
Vitamin D2 (ergocalciferol): Plant-based, but less effective.
Vegan D3: Derived from lichen, a good option for plant-based diets.

Always consult your healthcare professional before starting any supplements. You need enough vitamin D for good health, but taking too much can be harmful since the body stores it rather than excreting it.

How the Smith Biomed Vitamin D Test Works

Want to check your vitamin D levels at home? The Smith Biomed Vitamin D Test Kit is designed to be accurate and straightforward:

Collect a small blood sample by using the finger-prick tool included in the kit.
Apply the blood sample to the test cassette. Just a few drops are enough.
Add the buffer solution. This helps the test process the sample.
Wait 10 minutes for the result. A clear indicator line will show your vitamin D status.

It’s fast, discreet, and can be done from the comfort of your home. If your results show low levels of vitamin D, consult your GP or healthcare provider for further guidance on next steps.

Take Charge of Your Vitamin D Levels

To recap:

Deficiency develops from low sunlight, poor diet, or absorption issues
What vitamin D does for the body includes supporting bones, immunity, and mood.
Symptoms of low vitamin D range from fatigue to frequent infections.
Testing and the right supplement are the safest ways to restore healthy levels.

If you’ve been feeling run-down, consider testing your vitamin D levels. Could your tiredness simply be your body asking for more sunlight?

FAQ: Vitamin D Deficiency (Quick Answers)

Q: How does vitamin D deficiency occur?
A: It develops when sun exposure, diet, or absorption can’t keep up with the body’s needs.

Q: What does vitamin D do for the body?
A: It strengthens bones, supports immunity, regulates mood, and boosts muscle health.

Q: Where is vitamin D stored in the body?
A: Mainly in the liver and fat tissue.

Q: What are the signs when vitamin D is low?
A: Fatigue, muscle weakness, bone pain, frequent illness, and low mood.

Q: Which vitamin D supplement should I take?
A: Vitamin D3 is most effective for most people; vegan D3 is available for plant-based diets.

Q: Why is vitamin D important?
A: It underpins bone strength, immune defences, and overall vitality.

Q: How can I test my vitamin D levels?
A: The most reliable way is through a blood test. For a simple option, try the Smith Biomed at-home Vitamin D Test Kit, available at your local pharmacy.