GC Gene Variant rs1155563: What Your Genotype Means
The genetic variant rs1155563 is located within the GC gene, which provides instructions for making the vitamin D binding protein. Research indicates that this specific variant is associated with variations in circulating 25-hydroxyvitamin D concentrations in the blood.
What each genotype means
Typical vitamin D binding
This genotype represents the common variant at this position in the GC gene. Research indicates that this variant influences circulating 25-hydroxyvitamin D concentrations, though individual levels are also heavily dependent on environmental factors like sun exposure and dietary intake. If you have concerns about your vitamin D status, please discuss testing and potential supplementation with your healthcare provider.
This is a common genotype found across many global populations, though exact frequencies vary significantly by ancestry.
Varied vitamin D binding
This genotype involves one copy of the minor allele, which has been associated with differences in vitamin D binding protein affinity and circulating vitamin D levels. Because vitamin D status is influenced by a complex interplay of genetics, diet, and lifestyle, this result does not predict a specific health outcome. Please consult with your clinician to determine if your vitamin D levels are optimal based on your personal health history.
This heterozygous genotype is observed frequently in diverse populations, with prevalence rates that differ based on ancestral background.
Potential vitamin D variance
Carrying two copies of the minor allele at this position is associated with altered vitamin D binding protein characteristics and may correlate with lower circulating 25-hydroxyvitamin D concentrations in some studies. This association is statistical in nature and does not account for all factors affecting your vitamin D levels. You should discuss your vitamin D status and any need for supplementation with your healthcare provider.
This genotype is less common than the major allele homozygote and shows variable frequency across different ethnic and ancestral groups.
Understanding the rs1155563 Variant
The variant rs1155563 is a single nucleotide polymorphism (SNP) situated within the GC gene on chromosome 4. In genetics, a SNP represents a change in a single building block of DNA, known as a nucleotide. This particular variant is classified as intronic, meaning it resides in a non-coding region of the gene. While introns do not provide the direct instructions for building the protein's amino acid sequence, they often play critical roles in regulating how genes are expressed or processed. Scientists study these variants to understand how subtle differences in our DNA sequence can influence biological traits, such as the levels of specific proteins or metabolites circulating in our bodies. Because rs1155563 is located in the GC gene, it has been a subject of interest in studies investigating the genetic architecture of vitamin D metabolism.
The Role of the GC Gene
The GC gene encodes the vitamin D binding protein (VDBP). This protein is the primary carrier for vitamin D and its metabolites as they travel through the bloodstream. By binding to these molecules, the vitamin D binding protein helps regulate their availability, transport, and storage throughout the body. Beyond its transport function, VDBP is involved in various physiological processes, including the inflammatory response and the maintenance of bone health. Because the protein is essential for managing the body's vitamin D status, researchers have long investigated how genetic variations within the GC gene might alter the protein's structure, expression levels, or binding affinity. Understanding these mechanisms is important for researchers looking at how different individuals process and utilize vitamin D, which is a vital nutrient for immune function, calcium absorption, and overall metabolic health.
Research and Evidence
The association between rs1155563 and vitamin D levels has been explored in several large-scale genome-wide association studies (GWAS). These studies look for statistical correlations between specific genetic markers and measurable traits across large populations. Evidence suggests that rs1155563 is one of several variants in the GC gene region that correlate with serum 25-hydroxyvitamin D concentrations. However, it is important to note that the evidence strength for this specific variant is considered moderate. Genetic associations are complex; while a statistical link exists, it does not mean the variant is the sole cause of vitamin D level differences. Many factors, including diet, sun exposure, lifestyle, and other genetic variants, contribute significantly to an individual's vitamin D status. Consequently, researchers view this variant as a piece of a much larger puzzle rather than a definitive predictor of health outcomes.
What This Information Means for You
If you have received information about your rs1155563 genotype, it is important to interpret it within the context of your overall health. This variant is a tool for scientific research and population studies, not a diagnostic test for vitamin D deficiency or any specific medical condition. Because vitamin D levels are influenced by a wide array of environmental and lifestyle factors, your genotype alone cannot determine your current vitamin D status. You cannot use this information to diagnose yourself or to make decisions about supplementation or medical treatment. If you are concerned about your vitamin D levels or your general health, the most appropriate step is to consult with a healthcare professional. They can order standard blood tests to measure your actual vitamin D levels and provide personalized guidance based on your clinical history, rather than relying on genetic markers alone.
How common is this variant?
The frequency of the rs1155563 variant is variable across different ancestral populations, with a global minor allele frequency reported around 0.2365 in some datasets.
Frequently asked questions
Is rs1155563 a test for vitamin D deficiency?
No, rs1155563 is not a diagnostic test. It is a genetic variant associated with vitamin D metabolism in research studies, but it cannot determine your current vitamin D levels or diagnose a deficiency.
Should I take vitamin D supplements based on my genotype?
You should not change your health regimen based on this genetic variant. Always consult with your doctor or a registered dietitian to determine if supplementation is appropriate for your specific health needs.
What does the GC gene do?
The GC gene provides the instructions for creating the vitamin D binding protein. This protein is responsible for transporting vitamin D and its metabolites through the bloodstream to various tissues in the body.
Why is the evidence for this variant considered moderate?
The evidence is considered moderate because while statistical associations have been found in large studies, the biological impact of this specific intronic variant is complex and influenced by many other genetic and environmental factors.
Sources & further reading
Educational information only, last refreshed 10/1/2026. Not medical advice — these associations describe population statistics, not individual predictions.
Curious what your genotype is for rs1155563?
Upload a raw DNA file from 23andMe, AncestryDNA, MyHeritage, or FamilyTreeDNA and see this variant — plus thousands more — interpreted in your full report.
Get my report — $29Related variants in GC
One of the two primary SNPs in the Vitamin D Binding Protein gene that determines a person's Vitamin D status and transport efficiency.
This common regulatory variant near the GC gene is strongly associated with circulating serum 25-hydroxyvitamin D concentrations.
Common missense polymorphism in the vitamin D-binding protein gene that significantly alters circulating 25-hydroxyvitamin D concentrations.
Common missense variant Thr436Lys in the vitamin D binding protein gene strongly associated with reduced circulating serum 25-hydroxyvitamin D concentrations.