Lifestyle
- Increase sunlight exposure
- Engage in outdoor activities
- Monitor skin health
25-Hydroxyvitamin D · Calcidiol · Cholecalciferol · 25-OH-D3
25(OH)D quantifies the concentration of 25-hydroxyvitamin D in the blood, reflecting vitamin D status.
Standard ranges may vary by assay method; LC-MS is the gold standard.
Vitamin D3 (25-OH), also known as 25-Hydroxyvitamin D, Calcidiol, or Cholecalciferol, is a vital biomarker that measures the concentration of vitamin D in the blood. It is the primary 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 and supplements. Clinically, 25(OH)D is crucial for assessing bone health, as it plays a significant role in calcium and phosphate metabolism. Researchers have found that adequate levels of vitamin D reduce the risk of bone fractures, falls, and certain chronic diseases such as cardiovascular disease, type 2 diabetes, and some cancers. Additionally, vitamin D insufficiency is linked to autoimmune diseases and mood disorders, including postpartum depression. In the context of athletic performance and biohacking, maintaining optimal levels of 25(OH)D is associated with improved muscle function, immune support, and potentially enhanced testosterone levels in men. Researchers observed that vitamin D supplementation could increase testosterone levels, which may benefit athletes and individuals focused on longevity. However, there are caveats to consider, such as the variability in assay methods, which can affect measurement accuracy. Time of day and fasting status do not significantly impact 25(OH)D levels, but individual factors like skin pigmentation, geographic location, and season can influence vitamin D synthesis. Therefore, personalized assessment and intervention are recommended to achieve and maintain optimal vitamin D status.
Klinische Bedeutung
Elevated 25(OH)D levels may indicate excessive supplementation or sunlight exposure, while low levels suggest deficiency, increasing the risk of bone disorders and chronic diseases.
Progressively rising 25(OH)D levels suggest excessive supplementation or sunlight exposure; re-test in 3 months.
Progressively falling levels may indicate inadequate intake or absorption issues.
Re-test Interval
3 months if outside optimal range
Note:
Consult a healthcare provider before starting supplements, especially if on medication.
Vitamin D levels can vary throughout the day; morning testing is recommended for consistency.
Testing Frequency
Annually for healthy adults, more frequently if at risk of deficiency.
Correlated with
Current research suggests that there is significant variability among different assays for measuring 25-hydroxyvitamin D, leading to debates over reference ranges and optimal targets for vitamin D status. Researchers have not yet established the precise relationship between vitamin D levels and various health outcomes, such as postpartum depression and testosterone levels. Additionally, clinical questions remain unanswered regarding the long-term effects of vitamin D supplementation and the impact of confounding factors like vitamin D binding protein levels.
939
Total Citations
8
Human/RCT
2.8
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, bioactive testosterone, and free testosterone levels compared to the placebo group. The findings suggest a potential link between vitamin D levels and testosterone production.
Researchers discussed the critical role of calcium and phosphate in body functions and how vitamin D regulates their homeostasis. The study highlights the importance of laboratory tests for diagnosing metabolic bone diseases and the need for standardized protocols in measuring biomarkers related to calcium and phosphate metabolism.
This review examined the epidemiology of vitamin D and its association with various health conditions. Researchers found that vitamin D levels are linked to reduced risks of bone fractures, autoimmune diseases, and certain cancers. The study emphasizes the importance of maintaining sufficient vitamin D levels through sunlight exposure or supplementation.
This review examined the association between vitamin D deficiency and cardiovascular disease. Researchers found that low vitamin D levels may activate pro-inflammatory mechanisms that contribute to atherogenesis, 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
Researchers reviewed the historical development of methods for measuring serum 25-hydroxyvitamin D. The study noted the introduction of liquid chromatography-tandem mass spectrometry and emphasized the need for standardization to improve the reliability of vitamin D measurements across laboratories.
Researchers reviewed the clinical applications of 25-hydroxyvitamin D testing, noting its popularity due to links with various health conditions. The study emphasized the need for standardization of testing methods to reduce bias and improve the accuracy of vitamin D status assessments.
This study compared immunoassays and tandem mass spectrometry for measuring 25-hydroxyvitamin D levels. Researchers found significant differences among assays, highlighting the importance of harmonization in testing methods to ensure accurate diagnosis of 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.
10
Total Trials
5,075
Total Enrolled
American Laboratory Products Company
80
2026
Equivalence of 25-hydroxyvitamin D [25(OH)D] measurements between fresh and stored specimens
University College Cork
128
2025
Serum concentrations of 25-hydroxyvitamin D (25(OH)D)
Quadram Institute Bioscience
76
2025
Change in plasma lycopene and beta carotene to assess adherence
Ataturk University
83
2022
Measurements of 25(OH)D
Hanmi Pharmaceutical Company Limited
3,907
2017
The EuroQol EQ-5D
Sheffield Teaching Hospitals NHS Foundation Trust
112
2015
Free 25(OH)D
Oklahoma State University
240
2014
Plasma 25(OH)D concentrations of lactating women
University of Tromso
78
2013
Free fraction of 25(OH)D
Bispebjerg Hospital
43
2010
Change in serum 25(OH)D
Dana-Farber Cancer Institute
328
2007
Levels of Plasma 25(OH)D at Baseline, 3 Months and 6 Months.
Research publications about Vitamin D3 (25-OH) over time
10totalLog lab results, track trends and optimize your biomarkers over time.
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