Lever
Lifestyle
- Increase sun exposure
- Engage in outdoor activities
- Regular exercise
Blutwerte · Marker
Vitamin D3 (25-OH)
25-Hydroxyvitamin D · Calcidiol · Cholecalciferol · 25-OH-D3
Vitamine & Nährstoffe
- Einheit:
- nmol/L
- Abbreviation
- 25(OH)D
25-hydroxyvitamin D (25(OH)D) quantifies the circulating levels of vitamin D3, reflecting vitamin D status in the body.
Reference Ranges
Reference
50–125nmol/L
50
75
100
125
LowNormalHigh
Reference
Optimal
Unit · nmol/LStandard ranges may vary slightly by laboratory and geographic location.
Overview
Übersicht
Vitamin D3 (25-OH), also known as 25-hydroxyvitamin D or calcidiol, is a crucial biomarker for assessing vitamin D status in the body. It is the primary circulating form of vitamin D and is produced in the liver from vitamin D3 (cholecalciferol), which is synthesized in the skin upon exposure to sunlight or obtained from dietary sources. Researchers have found that 25(OH)D is tightly bound to vitamin D binding protein and albumin in the blood, with only a small fraction existing in a free form. Clinically, 25(OH)D levels are indicative of vitamin D sufficiency or deficiency, which can affect bone health, immune function, and calcium-phosphate metabolism. Deficiency is linked to conditions such as osteoporosis, osteomalacia, and rickets, while optimal levels are associated with improved bone density and reduced fracture risk. In the context of athletic performance and biohacking, maintaining adequate 25(OH)D levels is thought to support muscle function, reduce inflammation, and potentially enhance testosterone levels in men. However, researchers have observed that vitamin D status can vary with factors such as geographic location, season, and individual differences in skin synthesis capacity. Caveats include the need for standardized testing methods, as variability between assays can affect reliability. Additionally, time of day and fasting status may influence test results, though fasting is not typically required for 25(OH)D measurement.
Klinische Bedeutung
Reduced 25(OH)D levels indicate vitamin D deficiency, which can lead to bone disorders such as osteoporosis and rickets. Elevated levels are generally not associated with toxicity unless extremely high, which can cause hypercalcemia.
Dynamics
Trend Interpretation
Rising Values
Progressively rising 25(OH)D levels suggest improved vitamin D status; re-test in 6 months if levels exceed 125 nmol/L.
Falling Values
Falling 25(OH)D levels may indicate worsening vitamin D status or increased need; consider lifestyle or dietary changes.
Re-test Interval
6 months if outside optimal range
Etiology
Causes — High & Low
Cause
Elevated Levels
- Excessive supplementation
- High dietary intake
- Granulomatous diseases
- Williams syndrome
- Primary hyperparathyroidism
Cause
Low Levels
- Inadequate sun exposure
- Poor dietary intake
- Malabsorption syndromes
- Chronic kidney disease
- Liver disease
Protocol
How to Optimize
Lever
Nutrition
- Consume fatty fish
- Include fortified foods
- Eat egg yolks
Lever
Supplementation
- Vitamin D3 supplements
- Cod liver oil
- Multivitamins with vitamin D
Note:
Consult a healthcare provider before starting supplementation, especially if taking other medications.
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 deficient or during supplementation.
Interfering Factors
- Recent vitamin D supplementation
- Liver dysfunction
- Renal impairment
Related Peptides & Hormones
Testosterone
hormoneCorrelated with
Open Research Questions
Current research suggests that reference ranges for 25-hydroxyvitamin D (25[OH]D) may vary significantly based on population demographics and individual factors such as vitamin D binding protein levels, which remain understudied. Researchers have not yet established optimal targets for vitamin D supplementation in relation to testosterone levels or bone health. Additionally, clinical questions regarding the long-term effects of varying 25(OH)D levels on metabolic bone diseases and immune function remain unanswered.
23 Research Publications
800
Total Citations
7
Human/RCT
2.8
Avg. Influence
2025
Latest
Sort
Filter
01Top
#01
Effect of vitamin D supplementation on testosterone levels in men.
HumanInfluence13.0
313
This study evaluated the impact of vitamin D supplementation on testosterone levels in healthy overweight men. Researchers observed a significant increase in 25-hydroxyvitamin D (25[OH]D) levels and total testosterone levels in the vitamin D group compared to the placebo group. The findings suggest that vitamin D supplementation may positively influence testosterone levels.
02Top
#02
Calcium and Bone Metabolism Indices.
ReviewInfluence5.0
125
This study discussed the regulation of calcium and phosphate metabolism and the role of vitamin D. Researchers found that laboratory tests measuring calcium, phosphate, parathyroid hormone, and 25-hydroxyvitamin D (25[OH]D) are crucial for diagnosing metabolic bone diseases. They emphasized the importance of standardizing sample collection protocols for accurate bone turnover marker assessments.
03Top
#03
Vitamin D in Cardiovascular Disease.
ReviewInfluence1.0
67
This review explored the role of vitamin D in cardiovascular disease. Researchers found associations between vitamin D deficiency and increased inflammatory mechanisms contributing to atherosclerosis. However, the utility of 25-hydroxyvitamin D (25[OH]D) as a biomarker for predicting cardiovascular disease risk remains uncertain.
04
#04
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
This study focused on the clinical significance of measuring vitamin D and its metabolites. Researchers found that plasma concentrations of 25-hydroxyvitamin D (25[OH]D) are the best indicators of vitamin D deficiency. They also highlighted that vitamin D supplementation is recommended for individuals with low 25(OH)D levels, especially during certain months in Europe and North America.
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.
05
#05
Measurement of circulating 25-hydroxyvitamin D: A historical review.
ReviewInfluence1.0
53
Researchers reviewed the historical development of methods for measuring circulating 25-hydroxyvitamin D. They emphasized the need for standardization across different measurement techniques to ensure accurate clinical assessments of vitamin D status.
06
#06
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 (25[OH]D). Researchers found that both methods are widely used, but significant differences in results persist across laboratories. They emphasized the need for harmonization of testing methods to ensure accurate vitamin D deficiency diagnoses.
07
#07
Serum Vitamin D as a Biomarker in Autoimmune, Psychiatric and Neurodegenerative Diseases.
ReviewInfluence1.0
29
This narrative review examined the association between serum 25-hydroxyvitamin D (25[OH]D) levels and autoimmune, psychiatric, and neurodegenerative diseases. Researchers observed a correlation between low 25(OH)D levels and the prevalence of these diseases, but the clinical utility of 25(OH)D as a biomarker remains unclear due to variability in study methodologies.
08
#08
Vitamin D in adolescents: Are current recommendations enough?
ReviewInfluence2.0
25
This review addressed the importance of vitamin D for bone development during adolescence. Researchers noted a high prevalence of vitamin D deficiency in adolescents and highlighted the lack of consensus on adequate 25-hydroxyvitamin D (25[OH]D) levels. They suggested that current intake recommendations may need to be reassessed to ensure adequate vitamin D status.
09
#09
Effects of Vitamin D and K on Interleukin-6 in COVID-19.
HumanInfluence1.0
24
This study assessed the relationship between vitamin D and interleukin-6 levels in hospitalized COVID-19 patients. Researchers found that while vitamin D levels did not significantly differ between good and poor outcomes, higher IL-6 levels were associated with poorer clinical outcomes.
10
#10
Clinical Significance of Analysis of Vitamin D Status in Various Diseases.
Review
23
This article reviewed the clinical significance of vitamin D status in various diseases. Researchers found that measuring vitamin D levels can aid in diagnosing conditions like metabolic syndrome and cancer. They also noted that factors such as socio-demographic variables and genetic polymorphisms can affect vitamin D concentration interpretations.
Publication Trend
Research publications about Vitamin D3 (25-OH) over time
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