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Vitamin D deficiency is characterized by low serum vitamin D levels, although there is significant debate among professional societies over what level constitutes a deficiency. Causes include decreased cutaneous production of vitamin D, insufficient dietary intake, inadequate gastrointestinal absorption, impaired vitamin D metabolism (i.e., decreased activation, increased deactivation), and excessive losses. Patients are typically asymptomatic unless the deficiency is severe, in which case symptoms of complications (e.g., rickets, osteomalacia, hypocalcemia) may develop. Screening for vitamin D deficiency should be performed in individuals with conditions placing them at increased risk (e.g., those causing impaired metabolism or absorption of vitamin D), and may be considered in certain population groups (e.g., individuals with obesity, who are pregnant and/or lactating, or who have darker skin pigmentation). 25-hydroxyvitamin D (25-OHD) is the best diagnostic marker for vitamin D deficiency. Additional diagnostic studies are performed if complications or underlying conditions are suspected. Management involves the administration of vitamin D in addition to treatment of any associated complications and/or underlying conditions. Ensuring adequate daily vitamin D intake, especially in patients at increased risk for vitamin D deficiency, can help prevent associated complications.
Causes of impaired vitamin D synthesis 
Inadequate cutaneous synthesis of vitamin D3
Inadequate exposure to UV radiation, e.g., due to:
- Living in sufficiently northern or southern latitudes (typically above or below 33 degrees)
- Residence in an institution
- Sunscreen use
- Skin covering for cultural or religious reasons
- Darker skin pigmentation 
- Older age 
The most common cause of vitamin D deficiency is inadequate exposure to UV radiation. 
Inadequate dietary intake
- Restrictive diets (e.g., vegan diets, avoidance of vitamin-D fortified foods such as dairy products) 
- Infants: Breast milk is low in vitamin D. 
Causes of impaired metabolism of vitamin D
- Medications: modulators, e.g.: ; 
Causes of impaired absorption of vitamin D 
Malabsorptive conditions can cause multiple dietary deficiencies, especially in (A, D, E, and K). These include:
- Cystic fibrosis
- Chronic pancreatitis
- Inflammatory bowel disease
- Celiac disease
- Roux-en-Y gastric bypass) (e.g.,
Other causes 
- Screening is recommended for asymptomatic individuals with: 
- Also consider screening in the following populations: 
- Screen using serum 25-OHD levels; see “Interpretation of serum 25-OHD levels” for further information.
- Obtain 25-OHD levels in individuals with any of the following: 
- Indications for screening for vitamin D deficiency
- Incidental findings of either:
- Consider additional testing if there is concern for:
Interpretation of serum 25-OHD levels 
- The Institute of Medicine and Endocrine Society have set different thresholds for vitamin D status and subsequent treatment.
- Individuals age ≥ 65 years and/or conditions associated with adverse outcomes in vitamin D deficiency, consider using the Endocrine Society thresholds.
- For all other individuals, consider using the Institute of Medicine (IOM) thresholds.
|Classification of vitamin D status |
|Vitamin D status||IOM ||Endocrine Society |
|Deficiency|| || |
|Insufficiency|| || |
|Sufficiency|| || |
A serum 25-OHD level of < 20 ng/mL usually requires treatment; some patients may benefit from treatment at < 30 ng/mL. 
Additional studies 
- Request the following laboratory studies in suspected osteomalacia/rickets; common laboratory findings in vitamin D deficiency include:
- If an alternative etiology is suspected (not increased intake/cutaneous production): Obtain diagnostic studies as indicated, e.g., liver chemistries, renal function tests.
- Malnutrition: Consider evaluating for additional micronutrient deficiencies, e.g., iron deficiency, folate deficiency. 
Initial management 
- Treat any underlying .
- Administer treatment doses of vitamin D.
- Most patients: cholecalciferol or ergocalciferol 
- Patients with obesity, malabsorption, or medication that affects vitamin D metabolism: high-dose cholecalciferol or ergocalciferol 
- Patients with impaired 1α-hydroxylation or glucocorticoid excess may require an activated form of vitamin D (e.g., calcitriol ). 
- Ensure adequate calcium intake throughout treatment. 
- Patients with rickets and/or osteomalacia may require additional treatment (see “Treatment for osteomalacia and/or rickets”).
Individuals with obesity or malabsorption syndromes, or who take medications that affect vitamin D metabolism, typically need higher doses of vitamin D and calcium (e.g., 2–3 times the normal treatment doses). 
Monitoring and follow-up 
- Determine the treatment goal based on individual patient characteristics. 
- Adults > 65 years and/or conditions associated with adverse outcomes in vitamin D deficiency: ≥ 30 ng/mL
- All other adults: ≥ 20 ng/mL may be sufficient.
- The following groups require monitoring during treatment: 
- Patients with extrarenal production of 1,25(OH)2D (e.g., with granulomatous diseases, lymphoma)
- Patients with primary hyperparathyroidism: Monitor calcium levels regularly during treatment.
- Recheck 25-OHD levels at the end of treatment for all patients.
- Electrolyte and metabolic abnormalities: See “Common laboratory findings in vitamin D deficiency.” 
- Bone changes
Conditions associated with adverse outcomes in vitamin D deficiency 
To prevent complications, patients with the following conditions may benefit from maintaining a higher vitamin D level (≥ 30 ng/mL).
- Primary hyperparathyroidism
- Chronic kidney disease
- Multiple sclerosis
We list the most important complications. The selection is not exhaustive.
- Vitamin D deficiency prevention relies on adequate dietary intake of vitamin D, as recommended sunscreen for skin cancer prevention prevents vitamin D from being synthesized in the skin. 
- Intake may be in the form of foods and/or supplements (usually both). 
- Foods high in vitamin D include: 
- Supplements are usually in the form of cholecalciferol or ergocalciferol. 
|Age||Recommended Vitamin D dietary intake |
|< 1 year|| |
|1–70 years|| |
|> 70 years|| |
Adults with ongoing 2–3 times the recommended daily intake (i.e., 1500–2000 IU/day).  may require