Vitamin D (25-Hydroxy)
Measures vitamin D levels in the body to assess bone health, immune function, and overall vitamin D status
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What this test measures
The 25-hydroxyvitamin D test measures the major circulating form of vitamin D in the body, which serves as the best indicator of vitamin D supply from both cutaneous synthesis and nutritional intake. Vitamin D exists in two major forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). 25 hydroxy vitamin D3 (cholecalciferol) is the vitamin D that the body makes naturally or absorbs from animal sources, while 25 hydroxy vitamin D2 (ergocalciferol) comes from fortified plant sources, and both forms work similarly in the body.
Vitamin D is essential for the body to use calcium and phosphorus to build bones and support healthy tissues. With chronic or severe vitamin D deficiency, declined calcium and phosphorus absorption by the intestines leads to hypocalcemia and secondary hyperparathyroidism. Vitamin D helps the body absorb calcium, which is one of the main building blocks of bone, and also has a role in nervous, muscle, and immune systems. This test evaluates vitamin D stores in the body and can help identify deficiency or excess levels that may affect bone health, immune function, and overall wellbeing.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals over the age of 65, as both skin production of vitamin D and gut absorption become lower with aging
- Those who are obese, have had weight-loss surgery, or have conditions that affect nutrient absorption like celiac disease, Crohn disease, or ulcerative colitis
- People who spend most of their time indoors, have darker skin pigmentation, or live in northern latitudes with limited sun exposure
- Individuals experiencing bone pain, muscle weakness, muscle aches, fatigue, or mood changes like depression
- Those with a personal or family history of rickets, osteoporosis, or bone fractures
- People with chronic kidney disease, liver disease, or taking certain medications that may affect vitamin D metabolism
What to expect
Preparation
Usually, fasting is not required for this test, but this may depend on the laboratory and testing method used. Individuals should follow any specific instructions provided by the testing facility regarding eating before the test.
Sample Type
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or syringe.
Collection
A trained phlebotomist will collect the blood sample at the laboratory. The procedure typically takes just a few minutes and involves minimal discomfort. No doctor visit required for this simple lab test.
Turnaround
Results are typically available within 1-3 business days after the sample is received at the laboratory.
Understanding your results
Vitamin D levels are measured as nanograms per milliliter (ng/mL), and experts typically recommend levels between 20-40 ng/mL or 30-50 ng/mL for optimal health. Most people with vitamin D deficiency don't notice any symptoms, and others may experience vague symptoms that could be signs of various conditions. The test results help healthcare providers assess whether vitamin D levels are adequate for supporting bone health and overall wellness.
| Population | Reference Range | Notes |
|---|---|---|
| Adults | 30-100 ng/mL | Many experts recommend maintaining vitamin D levels between 30-50 ng/mL for optimal health benefits |
| Deficiency | Less than 20 ng/mL | Vitamin D deficiency is defined as serum 25-hydroxy vitamin D levels below 20 ng/mL |
| Insufficiency | 21-29 ng/mL | Vitamin D insufficiency is defined as levels between 21 and 29 ng/mL |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
Low vitamin D levels can lead to serious health conditions. In adults, severe vitamin D deficiency may cause osteomalacia, which results in weak bones, bone pain, and muscle weakness. Low levels can cause muscle weakness and cramps, fatigue, and depression, and may lead the body to take calcium from bones, resulting in accelerated bone demineralization and potentially osteomalacia in adults. Even mild, chronic vitamin D deficiency can lead to chronic hypocalcemia and secondary hyperparathyroidism, increasing the risk of osteoporosis, falls, and fractures, particularly in older individuals.
What does a “High” result mean?
Higher-than-normal vitamin D levels (hypervitaminosis D) are most commonly caused by taking excessive vitamin D supplements. This can result in too much calcium in the blood (hypercalcemia), which may lead to symptoms and kidney damage. Vitamin D intoxication typically does not occur until blood levels are above 150-200 ng/mL and is associated with hypercalcemia, hypercalciuria, and often hyperphosphatemia. Symptoms of vitamin D toxicity may include increased thirst and urination, poor appetite, constipation, and other complications.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your vitamin D test results are completely confidential and handled with the highest level of privacy protection. Results are <u>not reported to your personal doctor</u> unless you specifically choose to share them. The test results are <u>not part of your medical records</u> and will <u>not appear on insurance statements</u> or explanation of benefits (EOB) forms. We understand that some individuals prefer to monitor their vitamin D levels privately, whether due to concerns about insurance implications or simply personal preference. Your test results belong to you alone. We do not share your information with employers, insurance companies, or government agencies. All testing is conducted through certified laboratories that follow strict confidentiality protocols, ensuring your health information remains secure and private. This confidential testing approach allows individuals to proactively monitor their vitamin D status and take appropriate steps to optimize their health without concerns about privacy or medical record documentation.
Frequently asked questions
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CPT Code: 82306
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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