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Vitamin D · Guide

Vitamin D: IU, mcg and what you really pay

How to convert IU to mcg, what the official upper limit is, and why the cheapest price per dose can be misleading.

Updated October 21, 2026 · 4 min read · Prices checked November 1, 2026, US

Colorful tablets

Vitamin D is one of the cheapest supplements per dose – a few cents. But labels use two units, and the lowest price per dose often comes from a softgel with far more vitamin D than the official upper limit.

IU to mcg: 1 mcg = 40 IU

On US labels, vitamin D has to be listed in mcg (micrograms – also written µg, as on our price lists). IU (international units) can be added in parentheses (FDA rule (opens in a new tab)). The front of the bottle often still leads with IU.

mcgIUNote
10 mcg400 IU
15 mcg600 IUNIH: recommended for adults up to 70
20 mcg800 IUNIH: recommended for adults over 70
25 mcg1,000 IU
50 mcg2,000 IU
100 mcg4,000 IUNIH: upper limit for adults
125 mcg5,000 IU
Source: NIH Office of Dietary Supplements (opens in a new tab)

What the NIH says

Recommended for adults: 15–20 mcg (600–800 IU) a day, from food and supplements together. The upper limit for adults is 100 mcg (4,000 IU) a day (NIH (opens in a new tab)).

232 of the 531 products we checked have more than 100 mcg in one serving – above the upper limit for adults. The price list marks them and shows them last.

How much vitamin D is in one servingNumber of products we checked with each amount (amounts with at least 10 products)
  • 10 mcg400 IU29
  • 25 mcg1,000 IU117
  • 50 mcg2,000 IU115
  • 62.5 mcg2,500 IU15
  • 100 mcg4,000 IU14
  • 125 mcg5,000 IU · over the upper limit161
  • 250 mcg10,000 IU · over the upper limit51
  • 1,250 mcg50,000 IU · over the upper limit15

Darker bars: up to the NIH upper limit for adults (100 mcg). Lighter bars: above it.

Why the lowest price per dose can mislead

We compare per 25 mcg (1,000 IU). The lowest cost per 25 mcg comes from high-dose softgels – but you can’t take part of a softgel. So compare products with the same amount per serving:

Lowest cost per 25 mcg, by amount per servingThe cheapest product with each amount – the more per softgel, the lower the price per 25 mcg
  • 10 mcgNOW Foods · Liquid · 1.1¢ a serving2.9¢
  • 25 mcgNOW Foods · Liquid · 1.2¢ a serving1.2¢
  • 50 mcgBluebonnet Nutrition · Liquid · 2.3¢ a serving1.2¢
  • 62.5 mcgNOW Foods · Softgels · 5.4¢ a serving2.2¢
  • 100 mcgCarlson · Liquid · 5.5¢ a serving1.4¢
  • 125 mcgVitamatic · Softgels · 2¢ a serving0.4¢
  • 250 mcgVitamatic · Softgels · 2.8¢ a serving0.28¢
  • 1,250 mcgCalifornia Gold Nutrition · Softgels · $0.12 a serving0.25¢

Gummies vs. softgels

Per 25 mcg, the gummies we checked cost from 0.28¢ to $0.43, the softgels from 0.25¢ to $0.25. Gummies also have sugar or sweetener – check the label.

Before you buy

  1. Look for mcg in the Supplement Facts – IU is in brackets.
  2. Compare the amount per serving with the upper limit above.
  3. Compare the cost per 25 mcg among products with the same amount per serving.

All 531 products, sorted by cost per 25 mcg: vitamin D prices.

Sources

Not medical advice

We compare prices and label data. Amounts we compare by are not recommendations. Talk to a doctor or pharmacist before taking supplements, especially if you are under 18, pregnant or on medication.

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