Vitamin D in Tromsø

Tromsø demonstrates polar-night and midnight-sun edge cases; low solar altitude can still limit modeled vitamin D production even when the sun remains above the horizon. Location affects possible vitamin D production from sunlight; it does not change the age-based dietary reference intake or determine whether a particular person needs a supplement.

See Tromsø's sunlight estimate in the calculator

What the monthly model shows

The chart uses latitude 69.6492°, longitude 18.9553°, and elevation 10 m. It is model version 2026.09 with reference year 2026. It is not a weather forecast or measured local UV record.

Modeled daily IU from 30 minutes between 10:00 and 14:00 local solar time, skin type II, long sleeves and pants (15% exposed), 40% cloud cover, grass surface, and SPF 0. Customize every input.
Monthly modeled vitamin D production and gap to adult RDA in Tromsø
MonthModeled sunlightGap to RDA*
January0 IU/day400 IU/day
February0 IU/day400 IU/day
March0 IU/day400 IU/day
April39 IU/day361 IU/day
May215 IU/day185 IU/day
June484 IU/day0 IU/day
July490 IU/day0 IU/day
August214 IU/day186 IU/day
September23 IU/day377 IU/day
October0 IU/day400 IU/day
November0 IU/day400 IU/day
December0 IU/day400 IU/day

*Mathematical gap after modeled sunlight and an assumed 200 IU/day from food. This is not a supplement recommendation.

How much vitamin D do adults need?

Norwegian guidance emphasizes diet and supplements when intake is insufficient, with needs varying by age and life stage. Use national guidance rather than importing a US dose.

Read the current Norwegian Directorate of Health guidance

Vitamin D and seasonal depression

Seasonal affective disorder is a form of depression related to seasonal changes in daylight. Low vitamin D can coexist with it, but research on vitamin D as a SAD treatment is mixed. Established options include clinician-guided light therapy, psychotherapy, and medication. Read the evidence guide to vitamin D and SAD.

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