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Vitamin D (25-Hydroxy)

Nutrition & Vitamins

5 minutesBlood draw

A blood test that measures the level of vitamin D in your body.

Duration
5 minutes
Sample Type
Blood draw ()
Results Timeline
2-3 business days
No special preparation required

How to Prepare

Follow these instructions to ensure accurate test results

No fasting required
You can eat and drink normally
Continue supplements
Take your regular vitamin D supplements as usual unless told otherwise

Day of Your Test

  • No special preparation needed
  • Wear comfortable clothing with easy arm access

What This Measures

To check for vitamin D deficiency or excess, which affects bone health and immune function.

  • •25-hydroxyvitamin D - the main form of vitamin D in blood
  • •Your body's vitamin D stores from sun exposure and diet
  • •Vitamin D status for bone and immune health

Why This Test Matters

Vitamin D is essential for calcium absorption, bone health, immune function, and may play roles in mood and disease prevention. Deficiency is common, especially in northern climates.

Normal Ranges

Deficient
May need supplementation
Below 20 ng/mL
Insufficient
May benefit from more vitamin D
20-29 ng/mL
Sufficient
Adequate levels
30-100 ng/mL
Potentially harmful
High; toxicity usually occurs at even higher levels
Above 100 ng/mL

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

After the Test

  • Resume all normal activities immediately
  • No restrictions

Understanding Results

If High

Very high vitamin D (above 100 ng/mL) is rare but can cause problems. Usually occurs from taking too many supplements.

If Low

Low vitamin D is common and can cause bone weakness, fatigue, and immune issues. Treatment includes supplements and increased sun exposure.

Good to Know

  • Vitamin D levels vary by season (lower in winter)
  • Sun exposure provides vitamin D but increases skin cancer risk
  • Dietary sources include fatty fish, fortified foods, and egg yolks
  • Dark skin, obesity, and certain conditions affect vitamin D absorption

Follow Up

  • •If deficient: supplementation and retest in 8-12 weeks
  • •If sufficient: annual monitoring is usually adequate
  • •Discuss optimal levels with your doctor based on your health conditions

Source: Test preparation information is based on standard clinical guidelines and laboratory best practices. This information is provided for reference purposes only and should not replace professional medical advice, diagnosis, or treatment. Always follow the specific instructions provided by your healthcare provider or laboratory.