Home›Vitamin D (25-Hydroxy)

Content created by

Written by

B.Pharm

Reviewed by

Dr. Swati Gupta (Anand)

MD Lab Medicine, MBBS

Want to know more?
Read our Editorial Policy

Vitamin D (25-Hydroxy)

Q: What are the causes of vitamin D deficiency?

Vitamin D deficiency can happen if you don’t get enough from food or sunlight, if your body can’t absorb it well, or if your kidneys can't activate it. It's more common in people with milk allergies, lactose intolerance, or those following vegan or vegetarian diets.

Q: What is the right time to get the Vitamin D (25-Hydroxy) test done?

The Vitamin D (25-Hydroxy) test can be done at any time of the day. However, you should stop taking vitamin D supplements before the test to get accurate results.

Q: Are there any risks associated with the Vitamin D (25-Hydroxy) test?

No, usually, there are no risks associated with this test. The blood sample is withdrawn with the help of a needle, and the process is fairly fast and relatively painless.

Q: Who should be tested for vitamin D?

Vitamin D 25 (OH) testing is recommended for people being treated for osteoporosis or those with low or high calcium levels. It’s also useful for patients with conditions like cystic fibrosis, Crohn’s disease, or after gastric bypass surgery. Testing is advised if there’s no improvement with vitamin D therapy. Others who may need it include the elderly with little sun exposure, breastfed infants, and anyone with signs of rickets or soft bones (osteomalacia).

Q: What are some of the common vitamin D benefits for the body?

Vitamin D is essential for strong bones, healthy teeth, and a strong immune system. It helps the body absorb calcium and phosphorus. Low levels can lead to bone problems like rickets, osteomalacia, and osteoporosis.

Q: What are some of the easily available vitamin D food sources for vegetarians?

Some of the easily available vitamin D sources for vegetarians include mushrooms, broccoli, carrots, apples, bananas, rice, whole wheat, dairy products like milk and cheese, and fortified cereals.

Q: What are the additional lab tests needed to be performed in case of abnormal vitamin D test results?

Additional tests that can help establish vitamin D deficiency include 24-hour urine calcium, parathyroid hormone total or bone alkaline phosphatase level, serum calcium, and serum phosphorus level.

Also known as Calcidiol, Vit D (25-OH)

₹499~~₹1550~~ 67% Off

You need to provide

Blood

This test is for

Male, Female

Earliest reports in

12 hours

Test Preparation

No special preparation is required.

Understanding Vitamin D (25-Hydroxy)

What is Vitamin D (25-Hydroxy)?

The Vitamin D (25-Hydroxy) test measures the level of 25-OH vitamin D in the body. Vitamin D helps absorb calcium and phosphorus, keeps bones and teeth strong, and supports the immune system. Measures your vitamin D levels to assess bone health, immunity, and overall wellness.

Vitamin D is a fat-soluble essential nutrient. It exists in two primary forms:

Vitamin D3 (Cholecalciferol): derived from animal sources
Vitamin D2 (Ergocalciferol): derived from plant sources; both perform similar functions.

The main sources of vitamin D3 are certain foods, dietary supplements, and exposure to ultraviolet B (UVB) radiation from sunlight. On the other hand, vitamin D2 is derived from products or supplements of plant origin, mushrooms, etc. Both forms are converted into 25-hydroxy D2 or D3 respectively in the liver. The Vitamin D (25-OH) test measures only the Total 25-OH D vitamin (i.e. D2+D3) and does not differentiate between the two forms.

As per an NCBI (National Center for Biotechnology Information) study, vitamin D deficiency is highly prevalent across all age groups in India. Insufficient vitamin D levels can increase susceptibility to the following conditions:

Fractures
Weakened muscles
Fatigue
Compromised immune function
Higher likelihood of chronic illnesses like diabetes

The Vitamin D (25-Hydroxy) test helps check if you have too little or too much vitamin D, which can happen due to deficiency or taking too many supplements. If such circumstances arise, it may be necessary to discontinue vitamin D supplements and seek medical advice.

Usually, no special preparation is required for this test. A regular diet before taking the test can be consumed. However, it is generally recommended to stop taking vitamin D supplements before the Vitamin D (25-Hydroxy) test, as these supplements may affect the accuracy of the test results.

Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. Talk to the doctor about specific test results. The test results will help them determine the medical condition, make recommendations for lifestyle modifications such as diet and exercise, prescribe medication if required to manage the condition, and formulate an overall treatment plan.

Lifestyle Tips to Support Healthy Vitamin D Levels:

☀️ Heliotherapy (Sunlight Exposure) or Healthy Sun Exposure: Spend some time outdoors under the sun (preferably in the morning). This helps your body naturally produce vitamin D.

🥙 Eat (Diet): Include vitamin D-rich foods such as eggs, mushrooms, salmon, fortified milk, and orange juice.

🏃 Activity (Exercise): Regular physical activity, especially outdoors, can support better vitamin D synthesis and bone health.

😓 Lifestyle (Stress): Manage stress through yoga or relaxation techniques, as stress can indirectly impact bone health.

👨‍⚕️ Talk to Your Doctor (Consult): Do not self-medicate and avoid taking high doses of vitamin D supplements.

🚬 Habits (Alcohol & Smoking): Limit alcohol and quit smoking, as these can affect vitamin D metabolism and bone strength.

What is Vitamin D (25-Hydroxy) used for?

The Vitamin D (25-Hydroxy) test can be done:

A. In Symptomatic Individuals

Bone or joint pain
Chronic fatigue
Muscle weakness or cramps
Susceptibility to frequent infections

B. In High-Risk Groups

Osteoporosis or other bone disorders
Inflammatory bowel disease
Malabsorption syndromes (e.g., celiac disease, Crohn’s)
Chronic kidney or liver diseases

C. In Special Population

Pregnant and lactating women
Elderly individuals
Infants receiving exclusive breastfeeding

D. In Individuals With Lifestyle-Related Risks

Limited sun exposure
Strict vegan diet
Obesity

What does Vitamin D (25-Hydroxy) measure?

The Vitamin D (25-Hydroxy) test measures the levels of vitamin D in the body. It is an essential nutrient that can be synthesized in the body upon healthy exposure to sunlight or absorbed from dietary sources. It majorly exists in two forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is present in plants, such as yeast or mushrooms, and is available as a supplement in fortified foods, and vitamin D3 is found in foods like cheese, green vegetables, mushrooms, egg yolks, and fatty fish.

Both forms of vitamin D (D2 and D3) need to undergo some chemical changes before being available for use in the body. These chemical changes take place in the liver or kidneys. The levels of 25-hydroxy vitamin D in blood are considered the best parameter to assess the vitamin D status of the body. This test measures the level of Total 25-OH vitamin D (D2+D3), but it does not differentiate between the two forms, as it is the major form of vitamin D that circulates in the blood.

Interpreting Vitamin D (25-Hydroxy) results

Interpretations

A lower vitamin D level than the normal reference range indicates vitamin D deficiency, which can be because of less sun exposure, dietary lack, or decreased absorption from the intestine.

A higher vitamin D level than the normal reference range indicates vitamin D intoxication, usually due to excess vitamin supplementation.

Range:

The vitamin D range is measured as nanograms per milliliter (ng/mL) or nmol/L and can vary from lab to lab.

Level	Reference range (ng/mL)
Deficiency	<20
Insufficiency	20-29
Sufficiency	30-100
Toxicity	>100

Note:

This test does not include a separate vitamin D2 and D3 level analysis.
There can be seasonal variation in 25 (OH) vitamin D levels, with values being 40-50% lower in winter than in summer. It is also influenced by sunlight, latitude, skin pigmentation, sunscreen use, and hepatic function.
25 (OH) vitamin D levels can vary with age.
25 (OH) vitamin D level is increased during pregnancy.

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Vitamin D (25-Hydroxy)

Frequently Asked Questions about Vitamin D (25-Hydroxy)

Q. What is the vitamin D test used for?

The vitamin D test is done to measure the amount of vitamin D in individuals with symptoms such as bone deformities, dysfunction of the immune system, muscle cramps, and dental abnormalities, and to monitor the adequacy of treatment in patients who are receiving vitamin D supplements.

Q. What are the signs and symptoms of low vitamin D levels?

Signs and symptoms of vitamin D deficiency may include fatigue, bone pain, depression, hair loss, muscle weakness, appetite loss, pale skin, and sleep disturbances.

Q. How much vitamin D is needed daily?

a) 0–12 months: 400 IU/day; b). Ages 1–70: 600 IU/day; c) Over 70: 800 IU/day. For adults with low levels (<30 ng/mL), 1,500–2,000 IU/day is advised to restore balance (as per Endocrine Society).

Q. What are the causes of vitamin D deficiency?

Vitamin D deficiency can happen if you don’t get enough from food or sunlight, if your body can’t absorb it well, or if your kidneys can't activate it. It's more common in people with milk allergies, lactose intolerance, or those following vegan or vegetarian diets.

Q. What is the right time to get the Vitamin D (25-Hydroxy) test done?

The Vitamin D (25-Hydroxy) test can be done at any time of the day. However, you should stop taking vitamin D supplements before the test to get accurate results.

Q. Are there any risks associated with the Vitamin D (25-Hydroxy) test?

No, usually, there are no risks associated with this test. The blood sample is withdrawn with the help of a needle, and the process is fairly fast and relatively painless.

Q. Who should be tested for vitamin D?

Vitamin D 25 (OH) testing is recommended for people being treated for osteoporosis or those with low or high calcium levels. It’s also useful for patients with conditions like cystic fibrosis, Crohn’s disease, or after gastric bypass surgery. Testing is advised if there’s no improvement with vitamin D therapy. Others who may need it include the elderly with little sun exposure, breastfed infants, and anyone with signs of rickets or soft bones (osteomalacia).

Q. What are some of the common vitamin D benefits for the body?

Vitamin D is essential for strong bones, healthy teeth, and a strong immune system. It helps the body absorb calcium and phosphorus. Low levels can lead to bone problems like rickets, osteomalacia, and osteoporosis.

Q. What are some of the easily available vitamin D food sources for vegetarians?

Some of the easily available vitamin D sources for vegetarians include mushrooms, broccoli, carrots, apples, bananas, rice, whole wheat, dairy products like milk and cheese, and fortified cereals.

Q. What are the additional lab tests needed to be performed in case of abnormal vitamin D test results?

Additional tests that can help establish vitamin D deficiency include 24-hour urine calcium, parathyroid hormone total or bone alkaline phosphatase level, serum calcium, and serum phosphorus level.

Q. What are some of the common side effects of vitamin D overdose?

Side effects of vitamin D deficiency include hypercalcemia, which in turn can lead to nausea, vomiting, muscle weakness, neuropsychiatric disturbances, pain, loss of appetite, dehydration, polyuria, excessive thirst, and kidney stones. In extreme cases, vitamin D toxicity causes renal failure, calcification of soft tissues throughout the body (including in coronary vessels and heart valves), cardiac arrhythmias, and even death.

Q. What is osteomalacia?

Osteomalacia is the softening of the bones due to demineralization (the loss of minerals) and, most notably, by the depletion of calcium from bone. It is a characteristic feature of vitamin D deficiency in adults. Osteomalacia can also be caused by poor dietary intake or poor absorption of calcium and other minerals needed to harden bones.

Q. What is osteoporosis?

Osteoporosis is a condition of fragile bones with increased susceptibility to fracture. Vitamin D and calcium deficiency are some of the leading causes of osteoporosis. Other risk factors can be genetics, lack of exercise, personal history of fracture as an adult, smoking, excessive alcohol consumption, history of rheumatoid arthritis, low body weight, and family history of osteoporosis. Usually, osteoporosis does not manifest itself until bone fractures occur. X-rays and bone mineral density tests can help diagnose osteoporosis.

Q. Is there any correlation between the nutrients vitamin D and calcium?

Optimal vitamin D levels are necessary to increase the efficiency of calcium absorption. Without adequate vitamin D, the body absorbs only 10% to 15% of dietary calcium. When the vitamin D levels are adequate, the intestinal calcium absorption increases to 30% to 40%.

+ more