Understanding Your Total Vitamin D Test
When a healthcare provider orders a vitamin D blood test, they are measuring the total serum concentration of 25-hydroxyvitamin D, also known as 25(OH)D. This is the most reliable indicator of your body's overall vitamin D stores and reflects the sum of both vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) levels.
Because your D2 level is assessed as part of this total, you cannot receive a specific numerical result for D2 alone. Instead, your result will be placed within a range that determines your overall vitamin D status. This crucial context is often misunderstood by patients who think they are only being tested for one type of vitamin D.
Recommended Ranges for Total Vitamin D (D2 + D3)
Medical organizations offer slightly different interpretations, but general consensus defines status based on the concentration of 25(OH)D in the blood, measured in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L). The Endocrine Society defines ranges for adults as:
- Deficiency: Levels below 12 ng/mL (30 nmol/L). This can put you at risk for conditions like rickets in children and osteomalacia (softening of the bones) in adults.
- Insufficiency: Levels between 12 and 20 ng/mL (30 to 50 nmol/L). This is generally considered inadequate for bone and overall health, though not a severe deficiency.
- Sufficiency: Levels at or above 20 ng/mL (50 nmol/L). Many experts, like those at the National Institutes of Health, consider this range adequate for most people's needs. Some suggest that optimal levels may be higher, often aiming for 30-50 ng/mL.
- Potential Toxicity: Levels above 50 ng/mL (125 nmol/L). These levels may be associated with adverse effects, especially with prolonged high intake.
Vitamin D2 vs. Vitamin D3: A Comparison
While both forms contribute to your overall vitamin D status, they have different origins and potencies. Understanding their differences is key to making informed dietary and supplementation choices.
| Feature | Vitamin D2 (Ergocalciferol) | Vitamin D3 (Cholecalciferol) |
|---|---|---|
| Primary Source | Plant-based sources, especially UV-exposed mushrooms and yeast, fortified plant milks, and cereals. | Animal-based sources, such as oily fish, fish liver oils, egg yolks, and fortified dairy. The body also synthesizes it from sun exposure. |
| Body Production | The body does not produce vitamin D2. | The body produces vitamin D3 in the skin when exposed to sunlight's UVB rays. |
| Effectiveness | Considered less effective at raising and sustaining blood levels of total vitamin D compared to D3. | Generally more potent and effective at raising and maintaining blood levels. |
| Common Use | Often found in plant-based and fortified vegan products, as well as some high-dose prescription supplements. | More widely available in over-the-counter supplements and more frequently found in fortified foods. |
Boosting Your Vitamin D Levels
If your test results show low total vitamin D, you have several options to address it. Your doctor will recommend the best approach based on the severity of your deficiency and your specific health profile.
Dietary Sources
- Vitamin D2: Consume UV-exposed mushrooms and look for fortified plant-based milk and cereals.
- Vitamin D3: Include fatty fish (salmon, trout, sardines), egg yolks, and fortified dairy milk or yogurt in your diet.
Safe Sun Exposure
- Your body produces vitamin D3 naturally when exposed to sunlight. For many, 10-30 minutes of sun exposure on arms and legs a few times a week can significantly boost levels.
- Remember that factors like skin pigmentation, latitude, and season affect production. The American Academy of Dermatology recommends prioritizing dietary sources and supplements to reduce skin cancer risk from sun exposure.
Supplementation
- Oral supplements, which can be either D2 or D3, are an effective way to correct and maintain healthy vitamin D levels.
- While some studies show D3 to be more effective, D2 is a suitable option, particularly for those on vegan diets.
- Dosages vary, so it is vital to consult with a healthcare professional to determine the right amount for your needs. The National Institutes of Health provides general recommendations, but personalized medical advice is best.
Risk Factors for Low Vitamin D
Several factors can increase your risk of developing a vitamin D deficiency, making regular monitoring of your levels more important:
- Limited Sun Exposure: Spending most of your time indoors or living at a higher latitude with less direct sunlight.
- Darker Skin Pigmentation: Melanin reduces the skin's ability to produce vitamin D from sunlight.
- Older Adults: The skin's efficiency in producing vitamin D decreases with age.
- Obesity: Body fat can bind some vitamin D, preventing it from circulating in the blood.
- Malabsorption Conditions: Conditions like Celiac disease, Crohn's disease, and cystic fibrosis can interfere with nutrient absorption.
- Certain Medications: Some drugs, including certain cholesterol and anti-seizure medications, can affect vitamin D levels.
Conclusion
Understanding what should my vitamin D2 levels be requires interpreting your total 25(OH)D blood test result. While vitamin D2 is a crucial component, the overall status is what dictates whether your levels are deficient, insufficient, or sufficient for optimal health. Maintaining adequate levels is vital for bone strength, immune function, and mood regulation. For personalized advice, interpretation of results, and a tailored treatment plan, always consult with a healthcare provider. For more information on vitamin D, consult the National Institutes of Health Fact Sheet.
