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Pure Encapsulations vs NOW Foods Iodine (2026)
Disclosure: We earn commissions on purchases made through our links. This never influences our scores. Editorial policy
The Verdict
Pure Encapsulations takes it on our rubric, 90 to 86 on our 0-100 execution score, and holds our Top Pick badge; NOW holds our Best Value badge. Pure Encapsulations wins transparency 25 to 20, purity verification 23 to 20, and dosing and form 24 to 23; NOW wins value 23 to 18 at roughly a fifth of the daily cost. In our view the form difference is worth the extra thirteen cents for anyone who needs the dose to actually be the dose, and worth nothing at all for someone taking a general insurance dose, which is exactly how our notes describe the NOW kelp tablet. The more useful question our profile raises is whether you need either one: if you eat iodized salt, dairy, seafood, or seaweed, it says you probably do not need a separate iodine supplement, since US population intake runs adequate to borderline.
If you are pregnant or breastfeeding it points to a prenatal containing 150mcg rather than a standalone product. And it warns that megadose iodine protocols are not supported by RCT evidence and can trigger Wolff-Chaikoff hypothyroidism or worsen Hashimoto's in susceptible people. Test urine iodine and thyroid labs with a physician before going anywhere near the upper limit.
Pure Encapsulations Iodine (Potassium Iodide) 225 mcg
Pure Encapsulations
NOW Foods Kelp 150 mcg (200 tablets)
NOW Foods
Head-to-Head Comparison
| Category | Pure Encapsulations Iodine (Potassium Iodide) 225 mcg Pure Encapsulations | NOW Foods Kelp 150 mcg (200 tablets) NOW Foods |
|---|---|---|
| Brand Score | 90/100Winner | 86/100 |
| Dosing & Form | 24/25Winner | 23/25 |
| Purity | 23/25Winner | 20/25 |
| Value | 18/25 | 23/25Winner |
| Transparency | 25/25Winner | 20/25 |
| Cost/Day | $0.16 | $0.03Winner |
| Dose/Serving | 225mcg | 150mcg |
| Form | Potassium iodide (vegetarian capsule) | Organic kelp (Laminaria) tablet |
| Third-Party Tested | ✓ Yes | ✓ Yes |
| Proprietary Blend | No | No |
Why This Comparison Matters
Two different answers to the same nutrient. Pure Encapsulations delivers 225mcg as potassium iodide, which our profile identifies as the standardized form used in clinical trials and prenatal vitamins. NOW delivers 150mcg from organic kelp, and our profile is direct that kelp iodine varies batch to batch while potassium iodide does not.
Pure Encapsulations runs Eurofins and Silliker third-party testing on finished product, is hypoallergenic and free of gluten, soy, dairy, and GMOs, and states the form and exact microgram amount per capsule, at 120 capsules for $19.50. NOW is NPA GMP audited with an in-house testing program and discloses the kelp species as Laminaria along with the iodine content per tablet, at 200 tablets for $6.99. Neither carries USP or NSF certification.
On cost, Pure Encapsulations is about $0.16 a day at 225mcg and NOW about $0.03 at 150mcg. For reference, our profile lists the RDA at 150mcg a day for non-pregnant adults, 220mcg in pregnancy, and 290mcg in lactation, with a tolerable upper limit of 1,100mcg a day from all sources.
Detailed Score Breakdown
Pure Encapsulations Iodine (Potassium Iodide) 225 mcg
Pure Encapsulations
225 mcg as potassium iodide - the standardized, well-absorbed form used in clinical trials and prenatal vitamins. Slightly above the 150 mcg RDA, still well under the 1,100 mcg upper limit.
Pure Encapsulations runs Eurofins/Silliker third-party testing on finished product. Hypoallergenic formulation - free of gluten, soy, dairy, GMOs. GMP+ quality system.
About $0.16/day at 225 mcg per cap - premium pricing for the precision and clean formulation.
Form specified as potassium iodide with exact mcg per cap. No proprietary blends. Hypoallergenic vegetarian capsule. Full disclosure on label.
The cleanest formulation in this category. Best pick for people with multiple food sensitivities or anyone who wants dose precision from potassium iodide rather than variable kelp.
NOW Foods Kelp 150 mcg (200 tablets)
NOW Foods
150 mcg of iodine from organic kelp - matches the adult RDA and the dose used in prenatal vitamins. Kelp delivers natural iodine but varies batch-to-batch.
NOW Foods is NPA GMP audited and runs an in-house testing program. No USP or NSF certification on this specific SKU.
About $0.03/day at 150 mcg per tablet from the 200-count bottle - among the cheapest reliable iodine options.
Kelp source (Laminaria spp.) and iodine content per tablet disclosed. No proprietary blends. Easier-to-swallow tablet format.
The default pick for anyone who wants a 150 mcg/day insurance dose without overpaying. Kelp is less precise than potassium iodide but adequate for population-level adequacy.
How We Compared These Products
Every product in our database is scored on four equally-weighted pillars: dosing accuracy and form quality, purity verification (third-party testing), cost per clinically effective dose (not cost per pill), and label transparency. Each pillar is worth 25 points for a total of 100.
Cost per effective dose is calculated using the clinically studied dose from published research, not the manufacturer's suggested serving. If a product requires multiple servings to reach the dose used in clinical trials, that cost is reflected in the value score.
For a full explanation of our scoring methodology, see our methodology page. Prices were last checked on the dates listed for each product and may have changed.
Frequently Asked Questions
Is potassium iodide better than kelp?
They differ on precision rather than on quality. Our profile says potassium iodide at 150 to 225mcg is the form used in clinical trials and prenatal vitamins, and that kelp is variable batch to batch. NOW's own notes acknowledge that variability while calling kelp adequate for population-level adequacy. That difference is most of why our dosing and form and purity verification pillars favor Pure Encapsulations, 24 to 23 and 23 to 20.
Which iodine supplement is cheaper per day?
NOW, at about $0.03 a day for 150mcg against Pure Encapsulations at about $0.16 for 225mcg. The bottles are $6.99 for 200 tablets and $19.50 for 120 capsules. Our value pillar scores that 23 to 18, the only pillar NOW wins.
How much iodine do the guidelines cite?
Our profile lists the RDA at 150mcg a day for non-pregnant adults, 220mcg in pregnancy, and 290mcg in lactation, with a tolerable upper limit of 1,100mcg a day from all sources. It also says that if you eat iodized salt, dairy, seafood, or seaweed you probably do not need a separate supplement, and that iodine status and thyroid labs should be tested with a physician before exceeding the upper limit.
More Iodine Comparisons
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FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.