2oz vs. 4oz Lugol's Iodine: Which Size Should You Buy?

Once you've settled on a strength, the next question is simple: how much do you go through in a month, and does the bigger bottle save you money?

The Short Answer

The 4oz bottle is exactly double the 2oz bottle — same trusted formula, same concentration, twice the volume. If you're taking a consistent daily dose and already know your strength, the 4oz size (a "60-day supply" at typical dosing) is the smart, economical choice for keeping your routine going.

2oz vs. 4oz: Which Should You Buy?

4oz bottles are available across most of our strengths — 2%, 7%, 10%, 15%, and 20% — so you can size up confidently once you know your strength.

How Long Each Size Lasts

A 2oz bottle holds about 59 mL and a 4oz bottle about 118 mL. How long either lasts depends on your strength and how many drops you use each day. As a rough guide, the 2oz bottle is sized as about a 30-day supply at a typical serving and the 4oz bottle about a 60-day supply. If you use fewer drops, or a higher strength that needs fewer drops, either bottle will last longer.

Working Out the Better Value

• Look up the price of the 2oz and 4oz bottle at your strength.
• Divide each price by the number of days it lasts at your usual serving.
• Compare the cost per day.

In most cases, the 4oz bottle costs less per day. Multi-packs of the 2oz size can narrow the gap, so compare those too. For the full math, see 2oz vs. 4oz Bottles: A Value Breakdown.

Other Things to Consider

• Freshness: if a bottle would take many months to finish, the 2oz size keeps your supply fresher. See Does Iodine Expire?
• Travel: the 2oz bottle is easier to pack.
• Switching strengths: if you might change strength soon, buy the smaller size until you're settled. Our concentration chart helps you convert between strengths.
• Packaging: one 4oz bottle uses less packaging than two 2oz bottles.

Frequently Asked Questions

Does the 4oz bottle last exactly twice as long as the 2oz?

Yes — since it's the same trusted formula at double the volume, a 4oz bottle lasts roughly twice as long as a 2oz bottle at the same daily dose.

Should a first-time buyer start with the 4oz size?

We recommend starting with a 2oz bottle at a lower percentage first, so you can confirm your preferred strength before sizing up.

Does Lugol's Solution lose potency over time once opened?

Iodine solutions are light- and air-sensitive over long periods, so a smaller bottle you'll finish sooner can help keep things fresh if you don't go through it quickly.

Shop Lugol's Solution — the traditional, trusted way people have supported their iodine intake for over 200 years.

This article is for general educational purposes only and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease, and is not a substitute for advice from a qualified healthcare provider — especially if you are pregnant, nursing, taking thyroid medication, or managing a thyroid condition.

Jessica Bennett covers practical buying decisions and dosing logistics for the Iodine Journal.

This article is part of our complete comparison guide to Lugol's Solution, Liquid Iodine, and Nascent Iodine.