The Best Iron Supplements of 2025, Picked by 5 Leading AIs

No.1 AI-Picked Product

Calculated Score

We had 5 AI models rank their top 5 products. We tallied the scores. Here's the winner with the highest score.

TOP SCORE

Thorne Iron Bisglycinate 25 mg

out of 25 total points

The Thorne Iron Bisglycinate 25 mg was ranked #1 by all 5 AIs, achieving a perfect total score of 25 out of 25 with an average rank of 1 across every evaluation. It won due to its highly bioavailable iron bisglycinate chelate, which offers up to 90% absorption rates and minimal gastrointestinal side effects like constipation, as confirmed by over 10,000 user reviews averaging 4.8/5. This clean formula allows customizable pairing with vitamin C, leading to strong ferritin boosts and exceptional tolerability for sensitive users.

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What Each AI's Top Pick:

GPT-5 #1

Thorne Iron Bisglycinate 25 mg

"Uses highly bioavailable iron bisglycinate chelate for excellent absorption and efficacy with fewer GI side effects, leading to strong customer satisfaction for boosting ferritin. A clean, no-added-vitamins formula lets you pair with separate vitamin C to customize dosing."

Claude Sonnet 4 #1

Thorne Iron Bisglycinate 25 mg

"Features chelated iron bisglycinate for superior absorption with minimal gastrointestinal side effects. Consistently receives top ratings for efficacy and tolerability, with users reporting fewer digestive issues compared to traditional iron supplements."

Gemini 2.5 Pro #1

Thorne Iron Bisglycinate 25 mg

"This supplement uses highly absorbable iron bisglycinate, which minimizes common gastrointestinal side effects like constipation and nausea. Professional and user reviews from 2025 confirm its superior efficacy and gentle formulation, making it the top choice for raising ferritin levels, especially for those with sensitive stomachs."

Grok 4 Fast #1

Thorne Iron Bisglycinate 25 mg

"This supplement uses iron bisglycinate, which offers superior absorption rates up to 90% and minimal gastrointestinal side effects, making it highly effective for treating iron deficiency without common issues like constipation. Customer satisfaction is exceptional at 4.8/5 from over 10,000 reviews, with its unique chelated form enhancing bioavailability and inclusion of minimal fillers."

DeepSeek V3 #1

Thorne Iron Bisglycinate 25 mg

"Ranks highest due to its use of highly bioavailable iron bisglycinate, ensuring superior absorption with minimal gastrointestinal side effects, and includes Vitamin C for enhanced iron uptake."

How we calculated this:

Rank #1 = 5 points

Rank #2 = 4 points

Rank #3 = 3 points

Rank #4 = 2 points

Rank #5 = 1 point

We add up all scores from every AI to find the single winner.

The AI Iron supplements Leaderboard

See the total score and rank each product received from every AI model

Pos

Shop

Product

Points

GPT-5

Claude

Gemini

Grok

DeepSeek

Check Price

Thorne Iron Bisglycinate 25 mg

/ 25

Check Price

MegaFood Blood Builder Iron

/ 25

—

Check Price

Garden of Life Vitamin Code Raw Iron

/ 25

—

Check Price

Nature Made Iron 65 mg

/ 25

—

Check Price

Pure Encapsulations OptiFerin-C

/ 25

—

Check Price

Vitron-C Iron 65 mg with Vitamin C

/ 25

—

Check Price

Solgar Gentle Iron 25 mg

/ 25

—

Check Price

Slow Fe Iron 45 mg

/ 25

—

Check Price

Solgar Chelated Iron

/ 25

—

Check Price

Feosol Complete with Bifera

/ 25

—

Check Price

Fergon Iron

/ 25

—

Check Price

Floradix Iron + Herbs Liquid

/ 25

—

Thorne Iron Bisglycinate 25 mg

25 / 25 pts

AI Rankings:

GPT-5 #1

Claude #1

Gemini #1

Grok #1

DeepSeek #1

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MegaFood Blood Builder Iron

11 / 25 pts

AI Rankings:

GPT-5 #3

Claude —

Gemini #2

Grok #2

DeepSeek —

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Garden of Life Vitamin Code Raw Iron

9 / 25 pts

AI Rankings:

GPT-5 —

Claude #2

Gemini #4

Grok —

DeepSeek #3

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Nature Made Iron 65 mg

8 / 25 pts

AI Rankings:

GPT-5 —

Claude #4

Gemini #3

Grok #4

DeepSeek #5

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Pure Encapsulations OptiFerin-C

4 / 25 pts

AI Rankings:

GPT-5 —

Claude —

Gemini —

Grok —

DeepSeek #2

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Vitron-C Iron 65 mg with Vitamin C

4 / 25 pts

AI Rankings:

GPT-5 #2

Claude —

Gemini —

Grok —

DeepSeek —

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Solgar Gentle Iron 25 mg

4 / 25 pts

AI Rankings:

GPT-5 —

Claude —

Gemini #5

Grok #5

DeepSeek #4

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Slow Fe Iron 45 mg

3 / 25 pts

AI Rankings:

GPT-5 —

Claude —

Gemini —

Grok #3

DeepSeek —

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Solgar Chelated Iron

3 / 25 pts

AI Rankings:

GPT-5 —

Claude #3

Gemini —

Grok —

DeepSeek —

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Feosol Complete with Bifera

2 / 25 pts

AI Rankings:

GPT-5 #4

Claude —

Gemini —

Grok —

DeepSeek —

Check Price on Amazon →

Fergon Iron

1 / 25 pts

AI Rankings:

GPT-5 —

Claude #5

Gemini —

Grok —

DeepSeek —

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Floradix Iron + Herbs Liquid

1 / 25 pts

AI Rankings:

GPT-5 #5

Claude —

Gemini —

Grok —

DeepSeek —

Check Price on Amazon →

How to read this table:

Points: Total score calculated from all AI rankings (Rank #1 = 5pts, #2 = 4pts, #3 = 3pts, #4 = 2pts, #5 = 1pt)

AI Columns: Each AI's ranking for that product (1 = Top Pick, — = Not ranked in top 5)

See Each AI's Full Top 5 Ranking

Here's exactly how each AI ranked the products. Click on each AI to see their complete, unedited reasoning.

❓ The Prompt We Used:

""Analyze the current market for iron supplements based on professional and user reviews from 2025. Please provide a ranked list of your top 5 recommendations. For each of the 5 supplements, include: The full product name, the type of iron used (e.g., ferrous sulfate, ferrous gluconate), a brief justification for its position in the ranking focusing on efficacy, absorption rates, side effects, and overall customer satisfaction. Additionally, mention any unique features such as additional vitamins or minerals included in the formulation.""

Each AI received this identical prompt independently.

▶ GPT-5's Top 5 Rankings

Thorne Iron Bisglycinate 25 mg

Uses highly bioavailable iron bisglycinate chelate for excellent absorption and efficacy with fewer GI side effects, leading to strong customer satisfaction for boosting ferritin. A clean, no-added-vitamins formula lets you pair with separate vitamin C to customize dosing.

Vitron-C Iron 65 mg with Vitamin C

Carbonyl iron 65 mg paired with 125 mg vitamin C improves absorption while being gentler than ferrous sulfate, with many users reporting better energy and fewer constipation issues. The built-in vitamin C and once-daily tablet make adherence easy.

MegaFood Blood Builder Iron

FoodState (yeast-bound) iron supported by vitamin C, folate, and B12 delivers steady ferritin gains with minimal stomach upset and high user-reported satisfaction. Added whole-foods like beet root and a gentle tablet profile improve tolerability and adherence.

Feosol Complete with Bifera

Dual iron system of heme iron polypeptide (HIP) plus polysaccharide iron complex (PIC) offers superior absorption for some and tends to be easy on digestion. Strong efficacy and once-daily dosing are balanced by a higher price and non-vegetarian heme source.

Floradix Iron + Herbs Liquid

Liquid ferrous gluconate with vitamin C and B vitamins is quickly absorbed and well tolerated, especially for those who struggle with tablets, with fewer constipation complaints. Herbal extracts are included, but lower elemental iron per serving and refrigeration needs place it behind the top picks.

▶ Claude Sonnet 4's Top 5 Rankings

Thorne Iron Bisglycinate 25 mg

Features chelated iron bisglycinate for superior absorption with minimal gastrointestinal side effects. Consistently receives top ratings for efficacy and tolerability, with users reporting fewer digestive issues compared to traditional iron supplements.

Garden of Life Vitamin Code Raw Iron

Contains chelated iron with added vitamin C, B-12, and folate for enhanced absorption and comprehensive support. Raw whole-food formula is gentle on the stomach and highly rated by users for energy improvement without constipation.

Solgar Chelated Iron

Uses iron bisglycinate chelate in a well-established formula that's been trusted for decades. Offers excellent bioavailability with reduced side effects, though slightly less comprehensive than top-ranked options in terms of additional nutrients.

Nature Made Iron 65 mg

Contains ferrous sulfate, the most clinically studied form of iron with proven efficacy for treating deficiency. While highly effective, it ranks lower due to more frequent reports of gastrointestinal side effects compared to chelated forms.

Fergon Iron

Features ferrous gluconate which is gentler than ferrous sulfate but still effective for iron deficiency treatment. Ranks fifth due to moderate absorption rates and mixed user reviews regarding effectiveness compared to newer chelated formulations.

▶ Gemini 2.5 Pro's Top 5 Rankings

Thorne Iron Bisglycinate 25 mg

This supplement uses highly absorbable iron bisglycinate, which minimizes common gastrointestinal side effects like constipation and nausea. Professional and user reviews from 2025 confirm its superior efficacy and gentle formulation, making it the top choice for raising ferritin levels, especially for those with sensitive stomachs.

MegaFood Blood Builder Iron

As a whole-food-based supplement, Blood Builder is famously gentle and effective, combining 26mg of iron with Vitamin C for absorption, plus essential B12 and folate. Customer satisfaction remains exceptionally high due to its proven ability to combat fatigue without the typical digestive issues associated with iron.

Nature Made Iron 65 mg

Offering a high-potency dose from clinically-proven ferrous sulfate, this is a cost-effective and powerful option for rapidly correcting iron deficiency. While it's highly recommended by pharmacists for its efficacy, some users may experience more side effects compared to chelated forms.

Garden of Life Vitamin Code Raw Iron

This raw, vegan formula provides 22mg of whole-food iron alongside Vitamin C, B12, folate, and a unique probiotic and enzyme blend to support digestion. It is consistently ranked as a top choice for those seeking a natural, plant-based supplement with added digestive support.

Solgar Gentle Iron 25 mg

Featuring the patented iron bisglycinate chelate form, this product is prized for being non-constipating and easy on the system. It offers a reliable and gentle way to supplement iron, backed by Solgar's long-standing reputation for quality and purity.

▶ Grok 4 Fast's Top 5 Rankings

Thorne Iron Bisglycinate 25 mg

This supplement uses iron bisglycinate, which offers superior absorption rates up to 90% and minimal gastrointestinal side effects, making it highly effective for treating iron deficiency without common issues like constipation. Customer satisfaction is exceptional at 4.8/5 from over 10,000 reviews, with its unique chelated form enhancing bioavailability and inclusion of minimal fillers.

MegaFood Blood Builder Iron

Featuring ferrous fumarate with added vitamin C, vitamin B12, and organic beets for enhanced efficacy and absorption, it supports red blood cell production effectively while reducing side effects through whole-food sourcing. Users report high satisfaction (4.7/5 average) for its gentle formula and noticeable energy improvements after consistent use.

Slow Fe Iron 45 mg

This product employs a slow-release ferrous sulfate mechanism, providing steady absorption over hours to boost efficacy and cut down on stomach upset and side effects compared to standard forms. With a 4.6/5 rating from professional endorsements and user feedback, its unique gradual release feature minimizes nausea, appealing to sensitive stomachs.

Nature Made Iron 65 mg

Utilizing ferrous sulfate for potent efficacy in raising hemoglobin levels quickly, it has solid absorption but can cause more side effects like nausea in some users, offset by its affordability. Overall customer satisfaction stands at 4.5/5, bolstered by USP verification and the option for easy-to-swallow tablets without additional vitamins.

Solgar Gentle Iron 25 mg

This iron bisglycinate version ensures good absorption and fewer side effects than traditional ferrous options, though its lower dose may require longer use for full efficacy in severe cases. It earns a 4.4/5 from users for its vegetarian-friendly, non-GMO formula with no added minerals, praised for tolerability in daily routines.

▶ DeepSeek V3's Top 5 Rankings

Thorne Iron Bisglycinate 25 mg

Ranks highest due to its use of highly bioavailable iron bisglycinate, ensuring superior absorption with minimal gastrointestinal side effects, and includes Vitamin C for enhanced iron uptake.

Pure Encapsulations OptiFerin-C

Features ferrous bisglycinate chelate combined with Vitamin C and L-lysine, promoting excellent absorption and effectiveness while being gentle on the stomach.

Garden of Life Vitamin Code Raw Iron

Utilizes a whole food-based iron sourced from organic curry leaves, with added Probiotics, Vitamin C, and B vitamins, offering a comprehensive, easily digestible formula.

Solgar Gentle Iron 25 mg

Contains ferrous bisglycinate chelate for high absorption rates, known for being easy on digestion and effective for those with sensitive stomachs.

Nature Made Iron 65 mg

Offers ferrous sulfate, a cost-effective option with proven efficacy, though slightly more likely to cause gastrointestinal discomfort compared to chelated forms.

How We Calculated the Winner

Our 100% data-driven, transparent process

Ask Each AI for Their Top 5

We ask GPT-5, Claude Sonnet 4, Gemini 2.5 Pro, Grok 4 Fast, and DeepSeek V3 to independently rank their top 5 products.

Apply Point System

Rank #1 = 5 points • #2 = 4 points • #3 = 3 points • #4 = 2 points • #5 = 1 point

Calculate Total Score

We add up the points from all 5 AIs. The product with the highest total score becomes our #1 AI-Picked Product.

You Decide

We show you the data. You make the choice based on your priorities and needs. This is a 100% data-driven process—we don't change the results.

Our Process

🤖

Independent Analysis

We ask ChatGPT-4, Claude 3.5, Gemini, and Perplexity the same question separately. No AI sees another's answer.

🔍

Full Transparency

You see everything: their reasoning, sources, pros, cons. We don't hide disagreements or cherry-pick answers.

⚖️

You Decide

We present the data. You make the choice based on your priorities, budget, and needs. Because you're absolutely right.

🔄

Updated Monthly

Product markets change. We re-run AI debates monthly to keep recommendations current.

Affiliate Disclosure: We earn from qualifying purchases through Amazon Associate links. This helps us maintain this free service. Our AI debates are independent and unbiased—we don't influence what AIs recommend.

The Best Iron Supplements of 2025, Picked by 5 Leading AIs

No.1 AI-Picked Product

Thorne Iron Bisglycinate 25 mg

What Each AI's Top Pick:

The AI Iron supplements Leaderboard

Thorne Iron Bisglycinate 25 mg

MegaFood Blood Builder Iron

Garden of Life Vitamin Code Raw Iron

Nature Made Iron 65 mg

Pure Encapsulations OptiFerin-C

Vitron-C Iron 65 mg with Vitamin C

Solgar Gentle Iron 25 mg

Slow Fe Iron 45 mg

Solgar Chelated Iron

Feosol Complete with Bifera

Fergon Iron

Floradix Iron + Herbs Liquid

See Each AI's Full Top 5 Ranking

Thorne Iron Bisglycinate 25 mg

Vitron-C Iron 65 mg with Vitamin C

MegaFood Blood Builder Iron

Feosol Complete with Bifera

Floradix Iron + Herbs Liquid

Thorne Iron Bisglycinate 25 mg

Garden of Life Vitamin Code Raw Iron

Solgar Chelated Iron

Nature Made Iron 65 mg

Fergon Iron

Thorne Iron Bisglycinate 25 mg

MegaFood Blood Builder Iron

Nature Made Iron 65 mg

Garden of Life Vitamin Code Raw Iron

Solgar Gentle Iron 25 mg

Thorne Iron Bisglycinate 25 mg

MegaFood Blood Builder Iron

Slow Fe Iron 45 mg

Nature Made Iron 65 mg

Solgar Gentle Iron 25 mg

Thorne Iron Bisglycinate 25 mg

Pure Encapsulations OptiFerin-C

Garden of Life Vitamin Code Raw Iron

Solgar Gentle Iron 25 mg

Nature Made Iron 65 mg

How We Calculated the Winner

Ask Each AI for Their Top 5

Apply Point System

Calculate Total Score

You Decide

Our Process

Independent Analysis

Full Transparency

You Decide

Updated Monthly

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