Lever
Lifestyle
- Increase sunlight exposure
- Engage in outdoor activities
- Monitor skin health
Blutwerte · Marker
Vitamin D3 (25-OH)
25-Hydroxyvitamin D · Calcidiol · Cholecalciferol · 25-OH-D3
Vitamine & Nährstoffe
- Einheit:
- nmol/L
- Abbreviation
- 25(OH)D
25(OH)D quantifies the concentration of 25-hydroxyvitamin D in the blood, reflecting vitamin D status.
Reference Ranges
Reference
50–125nmol/L
50
75
100
125
LowNormalHigh
Reference
Optimal
Unit · nmol/LStandard ranges may vary by assay method; LC-MS is the gold standard.
Overview
Übersicht
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.
Dynamics
Trend Interpretation
Rising Values
Progressively rising 25(OH)D levels suggest excessive supplementation or sunlight exposure; re-test in 3 months.
Falling Values
Progressively falling levels may indicate inadequate intake or absorption issues.
Re-test Interval
3 months if outside optimal range
Etiology
Causes — High & Low
Cause
Elevated Levels
- Excessive supplementation
- High sunlight exposure
- Granulomatous disorders
- Lymphoma
- Hyperparathyroidism
Cause
Low Levels
- Insufficient sunlight exposure
- Poor dietary intake
- Malabsorption syndromes
- Chronic kidney disease
- Liver disease
Protocol
How to Optimize
Lever
Nutrition
- Consume fatty fish
- Include fortified foods
- Increase egg yolk intake
Lever
Supplementation
- Vitamin D3 supplements
- Cod liver oil
Note:
Consult a healthcare provider before starting supplements, especially if on medication.
Testing Guidelines
✓Fasting Not Required
✓Not Time-Sensitive
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.
Interfering Factors
- Assay method variability
- Recent vitamin D supplementation
Related Peptides & Hormones
Testosterone
hormoneCorrelated with
Open Research Questions
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.
26 Research Publications
939
Total Citations
8
Human/RCT
2.8
Avg. Influence
2025
Latest
Sort
Filter
01Top
#01
Effect of vitamin D supplementation on testosterone levels in men.
HumanInfluence14.0
317
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.
02Top
#02
Calcium and Bone Metabolism Indices.
ReviewInfluence5.0
128
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.
03Top
#03
Epidemiology of vitamin D in health and disease.
ReviewInfluence2.0
87
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.
04
#04
Vitamin D in Cardiovascular Disease.
ReviewInfluence1.0
67
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.
05
#05
Measurement of vitamin D and its metabolites (calcidiol and calcitriol) and their clinical significance.
Schmidt-Gayk H, et al. · Scandinavian journal of clinical and laboratory investigation. Supplementum · 1997
Review
62
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
- 01Researchers observed that 25-hydroxyvitamin D is the best marker for assessing vitamin D deficiency.
- 02They found that many people in Europe and North America have suboptimal vitamin D levels from November to April.
- 03The study indicated that vitamin D metabolism is affected by kidney health and the body's calcium and phosphate supply.
06
#06
Measurement of circulating 25-hydroxyvitamin D: A historical review.
ReviewInfluence1.0
53
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.
07
#07
25-Hydroxyvitamin D: analysis and clinical application.
Review
38
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.
08
#08
25-Hydroxyvitamin D Testing: Immunoassays Versus Tandem Mass Spectrometry.
ReviewInfluence2.0
31
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.
09
#09
Serum Vitamin D as a Biomarker in Autoimmune, Psychiatric and Neurodegenerative Diseases.
ReviewInfluence1.0
30
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.
10
#10
Vitamin D in adolescents: Are current recommendations enough?
ReviewInfluence2.0
25
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.
Clinical Trials (10)
10
Total Trials
5,075
Total Enrolled
ALPCO 25(OH) Vitamin D CLIA Kit - Fresh Versus Frozen Serum and Plasma Stability Study
NCT07565064ENROLLING_BY_INVITATION
Sponsor
American Laboratory Products Company
Enrollment
80
Started
2026
Primary outcome
Equivalence of 25-hydroxyvitamin D [25(OH)D] measurements between fresh and stored specimens
Vitamin D DeficiencyVitamin D InsufficiencyHealthy Volunteers
A Household-Based Dietary Intervention Study of Vitamin D Fortified Bread in Irish Families
NCT07481240COMPLETED
Sponsor
University College Cork
Enrollment
128
Started
2025
Primary outcome
Serum concentrations of 25-hydroxyvitamin D (25(OH)D)
Vitamin D Deficiency
Investigating the Impact of Vitamin D Biofortified Tomatoes on Serum Levels of 25(OH)D
NCT07142759ENROLLING_BY_INVITATION
Sponsor
Quadram Institute Bioscience
Enrollment
76
Started
2025
Primary outcome
Change in plasma lycopene and beta carotene to assess adherence
Vitamin D Insufficiency
25-Hydroxyvitamin D Levels in Patients With Periodontitis (Stage III)
NCT05343273COMPLETED
Sponsor
Ataturk University
Enrollment
83
Started
2022
Primary outcome
Measurements of 25(OH)D
Vitamin D DeficiencyPeriodontitis
An Observational Study Assessing Effects in Patients With Combination Therapy With Raloxifene/Cholecalciferol
NCT04788290COMPLETED
Sponsor
Hanmi Pharmaceutical Company Limited
Enrollment
3,907
Started
2017
Primary outcome
The EuroQol EQ-5D
Osteoporosis
Change in Free 25(OH)D After High Dose in Vitamin D Deficient Postmenopausal Women
NCT02553044COMPLETED
Sponsor
Sheffield Teaching Hospitals NHS Foundation Trust
Enrollment
112
Started
2015
Primary outcome
Free 25(OH)D
Vitamin D DeficiencyOsteoporosis
Maternal Vit D Supplements & Infant and Maternal Biomarkers & Outcomes in Southern Ethiopia
NCT02210884COMPLETED
Sponsor
Oklahoma State University
Enrollment
240
Started
2014
Primary outcome
Plasma 25(OH)D concentrations of lactating women
Vitamin D Deficiency
Measurement of the Free Fraction of 25-hydroxyvitamin D in Serum
NCT01771380COMPLETED
Sponsor
University of Tromso
Enrollment
78
Started
2013
Primary outcome
Free fraction of 25(OH)D
Impaired Glucose Tolerance
The Influence of Skin Pigmentation on UVB Induced Vitamin D Increase
NCT03409510COMPLETED
Sponsor
Bispebjerg Hospital
Enrollment
43
Started
2010
Primary outcome
Change in serum 25(OH)D
Healthy Volunteers
Vitamin D for Chemoprevention
Sponsor
Dana-Farber Cancer Institute
Enrollment
328
Started
2007
Primary outcome
Levels of Plasma 25(OH)D at Baseline, 3 Months and 6 Months.
Gastrointestinal CancersProstate CancerHypertension
Publication Trend
Research publications about Vitamin D3 (25-OH) over time
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