Vitamin D deficiency is common, but the decision to supplement should be based on your own levels — not general recommendations alone.
A simple blood test measuring 25-hydroxyvitamin D gives your baseline. Levels below 20 ng/mL are generally considered deficient; between 20 and 30 ng/mL is often called insufficient. Above 30 ng/mL is adequate for most people.
For those with low levels, a daily supplement of 1000 to 2000 IU is a reasonable starting point for many adults, though your doctor may recommend higher doses for a defined correction period.
Sunlight remains the most natural source. Fifteen to thirty minutes of midday exposure on arms and legs several times a week can meaningfully raise levels, depending on your skin tone and location.
Do not self-supplement at very high doses without monitoring. Vitamin D toxicity, though rare, causes real harm and is entirely preventable with periodic testing.