Why Don't Doctors Recommend Vitamin D?

Vitamin D is essential for bone health and has attracted attention for potential roles in immunity, mood, and chronic disease prevention. Despite popular interest, many clinicians take a cautious stance on routine supplementation. This article outlines the science behind those reservations and practical guidance for patients and clinicians.

Established roles and uncertainties

Vitamin D (measured as serum 25-hydroxyvitamin D [25(OH)D]) is crucial for calcium absorption and bone mineralization. Deficiency causes rickets in children and can contribute to osteomalacia and fracture risk in adults. Beyond skeletal effects, observational studies suggest links between vitamin D status and immune function, cardiovascular health, and mood, but randomized trials have produced mixed or inconclusive results for many non-skeletal outcomes.

Why clinicians are cautious

Several practical and evidence-based reasons explain why doctors may not recommend supplements universally: clinical thresholds for deficiency vary; evidence for prevention of chronic diseases is inconsistent; supplement quality and dosing can be variable; and high or unsupervised doses carry risks such as hypercalcemia and kidney injury. For these reasons many clinicians prefer a targeted test-and-treat approach rather than blanket supplementation.

Testing and target levels

Most guidelines use serum 25(OH)D to assess status. Cutoffs differ between organizations: values below ~30 nmol/L are widely considered deficient, while levels above 50 nmol/L are often called sufficient for bone health. Some practitioners aim for higher targets, which contributes to debate about when to treat and how aggressively.

Sun exposure and practical considerations

Sunlight is the primary natural source of vitamin D, but synthesis varies by latitude, season, skin pigmentation, age, and clothing. Dermatologic concerns about UV exposure create a tension between sun protection and vitamin D synthesis. For people with limited sunlight or higher risk of deficiency, measured supplementation may be the safer option.

Supplementation: forms and safety

Cholecalciferol (vitamin D3) is generally more bioavailable than ergocalciferol (D2). Low-dose supplementation is usually safe for most adults, but high-dose regimens should be guided by a clinician and follow-up testing. Given variability in over-the-counter product quality, clinicians emphasize reliable sourcing and appropriate monitoring.

Practical approach

Clinicians commonly recommend testing for patients with risk factors—older adults, limited sun exposure, darker skin, malabsorption syndromes, or bone disease—and then treating confirmed deficiency. This individualized strategy seeks to balance benefit and harm rather than applying a one-size-fits-all recommendation.

For a succinct overview of why clinicians weigh evidence carefully, see Why Don't Doctors Recommend Vitamin D?. For context on supplement quality and trusted brands, refer to this review on supplement quality and trusted brands. Related guidance on zinc supplementation and formulation choices can be found at zinc supplement guidance and a concise overview available on Telegraph Zinc Supplement: How to Choose.

Evidence evolves; clinicians update recommendations as higher-quality trials and meta-analyses become available. Until then, testing when indicated and individualized treatment remain the most consistent, evidence-aligned strategies.