sunup

Find the best time to get your daily vitamin D.

Skin Type

Type I

Very fair

Type II

Fair

Type III

Medium

Type IV

Olive/Brown

Type V

Dark Brown

Type VI

Deeply Pigmented
How much skin will be exposed?
Modifiers (optional)
About Vitamin D

There is significant disagreement between major health bodies on optimal vitamin D levels.

US RDA (Institute of Medicine, 2010)

600–800 IU/day. Target serum 25(OH)D: 20 ng/mL. Many researchers consider this insufficient to maintain optimal health.

Endocrine Society (2011)

1,500–2,000 IU/day to maintain levels > 30 ng/mL. Recommends up to 4,000–10,000 IU/day for deficient individuals under medical supervision.

GrassrootsHealth / Holick et al.

Many vitamin D researchers advocate for serum levels of 40–60 ng/mL, requiring 4,000–6,000 IU/day for most adults. The tolerable upper intake level is generally set at 10,000 IU/day.

Deficiency is typically defined as serum 25(OH)D below 20 ng/mL; insufficiency is 20–30 ng/mL. Effects can be subtle:

  • Bone health: Reduced calcium absorption; increased risk of osteoporosis, rickets in children, osteomalacia in adults
  • Immune function: Higher susceptibility to infections; potential role in autoimmune conditions
  • Mood & cognition: Associated with increased rates of depression, seasonal affective disorder, and cognitive decline
  • Muscle function: Weakness, fatigue, musculoskeletal pain
  • Cardiovascular: Observational links to hypertension and cardiovascular disease (causality debated)
  • Cancer risk: Some evidence for protective effects against colorectal, breast, and other cancers (ongoing research)
Vitamin D deficiency affects an estimated 40% of Americans and up to 1 billion people worldwide.

Sun exposure produces D3 directly in the skin and triggers additional photoproducts (like lumisterol and tachysterol) not present in supplements. Some researchers believe sun-derived vitamin D may be metabolized differently or have additional benefits.

However, sun exposure also carries UV damage risk. Supplements (D3 is preferred over D2) are a reliable, safe alternative — especially in winter, at northern latitudes, or for those with darker skin.

D3 vs D2: D3 (cholecalciferol) raises serum 25(OH)D more effectively than D2 (ergocalciferol) and is the recommended supplement form.

Cofactors: Vitamin K2 (MK-7 form) helps direct calcium appropriately. Magnesium is required for vitamin D activation — deficiency in either can limit effectiveness.

sunup is informational only. Consult a healthcare provider for personalized medical advice.