Lifestyle
- Increase sun exposure
- Engage in outdoor physical activities
- Monitor and adjust vitamin D supplementation
25-Hydroxyvitamin D · Calcidiol · Cholecalciferol · 25-OH-D3
The test quantifies the concentration of 25-Hydroxyvitamin D in the blood, reflecting vitamin D status.
Reference ranges may vary by assay method and population. Consider seasonal and geographic factors.
Vitamin D3 (25-OH), also known as 25-Hydroxyvitamin D or Calcidiol, is a prehormone produced in the liver by hydroxylation of vitamin D3 (cholecalciferol). It is the main circulating form of vitamin D and is considered the best indicator of vitamin D status in the body. This biomarker reflects the amount of vitamin D produced in the skin from sunlight exposure and obtained from dietary sources. Clinically, 25(OH)D is crucial for calcium and phosphate homeostasis, influencing bone health and immune function. Deficiency is linked to conditions such as osteoporosis, rickets, and increased susceptibility to infections. Epidemiological studies have also associated adequate levels with reduced risks of autoimmune diseases, cardiovascular diseases, and certain cancers. For athletes and biohackers, maintaining optimal levels of 25(OH)D is important for muscle function, immune modulation, and possibly enhancing testosterone levels, as some studies suggest a correlation between vitamin D supplementation and increased testosterone in men. However, researchers note that assay variability and factors like skin pigmentation, latitude, and seasonal changes can affect 25(OH)D levels. Time-of-day and fasting do not significantly impact the test, but standardization of assays is essential for accurate assessment.
Klinische Bedeutung
Elevated 25(OH)D levels may indicate excessive supplementation or hypercalcemia, while reduced levels suggest vitamin D deficiency, potentially leading to bone disorders and increased disease risk.
Progressively rising values may indicate excessive supplementation. Re-test in 3 months if levels exceed 125 nmol/L.
Falling values suggest worsening deficiency or malabsorption issues.
Re-test Interval
4 weeks if outside optimal range
Note:
Consult a healthcare provider before starting supplementation, especially if on medications affecting calcium metabolism.
Vitamin D levels can vary throughout the day; morning testing is recommended for consistency.
Testing Frequency
Annually for healthy adults, more frequently if managing deficiency.
Correlated with
Current research suggests that there is significant variability in 25-hydroxyvitamin D (25[OH]D) measurements across different immunoassays, leading to debates about reference ranges and optimal targets for vitamin D status, particularly in specific populations like pregnant women. Researchers have not yet established standardized protocols for vitamin D testing, which could address discrepancies in results. Additionally, unanswered clinical questions remain regarding the long-term health impacts of varying 25(OH)D levels on conditions like osteoporosis and autoimmune diseases.
938
Total Citations
8
Human/RCT
2.7
Avg. Influence
2025
Latest
This study examined the effect of vitamin D supplementation on testosterone levels in healthy overweight men. Researchers found that vitamin D supplementation significantly increased total testosterone levels, bioactive testosterone, and free testosterone compared to the placebo group. Initial vitamin D levels were in the deficiency range, highlighting the potential impact of supplementation.
Researchers discussed the critical role of calcium and phosphate in body functions, regulated by vitamin D and parathyroid hormone. The review emphasized the importance of laboratory tests, including 25-hydroxyvitamin D, in diagnosing metabolic bone diseases and monitoring calcium homeostasis.
This review explored the epidemiology of vitamin D in relation to various health conditions. Researchers found that adequate vitamin D levels are crucial for reducing risks of bone fractures, autoimmune diseases, and certain cancers, while noting widespread vitamin D insufficiency in high latitude populations.
This review explored the relationship between vitamin D and cardiovascular disease. Researchers found associations between vitamin D deficiency and increased inflammatory processes that may contribute to atherosclerosis, although the role of 25-hydroxyvitamin D as a biomarker for cardiovascular risk remains unclear.
Schmidt-Gayk H, et al. · Scandinavian journal of clinical and laboratory investigation. Supplementum · 1997
Researchers investigated the clinical significance of measuring vitamin D and its metabolites. They found that plasma concentrations of 25-hydroxyvitamin D (25[OH]D) are the best indicators of vitamin D deficiency. The study also highlighted that vitamin D supplementation is recommended for individuals with 25(OH)D levels below 50 nmol/L.
Key findings
This historical review examined the evolution of methods for measuring 25-hydroxyvitamin D. Researchers highlighted the introduction of liquid chromatography-tandem mass spectrometry as a more precise method, while also stressing the need for standardization to ensure consistent clinical decision thresholds.
This review focused on the clinical applications of 25-hydroxyvitamin D testing. Researchers noted that despite improvements in testing methodologies, significant biases exist among different assays, underscoring the need for standardization to accurately assess vitamin D status.
Researchers compared automated immunoassays and tandem mass spectrometry for measuring 25-hydroxyvitamin D. The study emphasized the need for harmonization of testing methods due to significant differences in results, which are critical for making clinical decisions regarding vitamin D deficiency.
Researchers summarized studies on serum 25-hydroxyvitamin D levels in autoimmune, psychiatric, and neurodegenerative diseases. They found an association between low 25(OH)D levels and the prevalence of these conditions, but the clinical utility of 25(OH)D as a biomarker remains unclear due to variability in study methods.
This review addressed the importance of vitamin D for bone development in adolescents. Researchers highlighted the high prevalence of vitamin D inadequacy in this population and noted that current intake recommendations may not be sufficient to achieve optimal 25-hydroxyvitamin D levels for bone health.
Research publications about Vitamin D3 (25-OH) over time
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