Supplement Comparison Tool
Different forms of the same supplement vary dramatically in absorption, cost, and effectiveness. Compare them side-by-side to find the best option for your needs and budget.
Select a Supplement to Compare
What the Comparison Tool does
Pick any two (or three) options and the tool puts them side-by-side on the things that actually matter:
- Bioavailability — how much of the dose your body can actually use.
- Best-for goal — which form has the strongest evidence for sleep, energy, anxiety, performance, etc.
- Side effect profile — GI tolerance, common reactions, who should avoid.
- Cost per effective dose (not per pill — per usable dose).
- Third-party testing status — NSF, USP, Informed Sport, or none.
It works two ways: compare forms of the same supplement (Magnesium Glycinate vs. Citrate vs. Threonate vs. Oxide), or compare brands of the same form (Thorne Glycinate vs. Doctor’s Best vs. NOW).
How to use it
- Pick a category at the top (e.g., Magnesium, Omega-3, Probiotics).
- Select 2 or 3 options to compare. The tool will surface the forms or brands most worth comparing.
- Set your goal if it’s goal-specific (sleep vs. constipation vs. exercise performance change which form wins).
- Scan the comparison table — winners on each criterion are highlighted.
- Click any row for the underlying detail (study citations, typical dose, etc.).
Examples
Example — Magnesium forms compared for sleep
| Glycinate | Citrate | Threonate | Oxide | |
|---|---|---|---|---|
| Bioavailability | High | Medium-High | Medium (brain-specific) | Very low (~4%) |
| Best for | Sleep, anxiety, muscle relaxation | Constipation, general | Cognition, memory | Almost nothing useful |
| GI side effects | Minimal | Loose stools at higher doses | Minimal | Common |
| Cost / effective dose | $$ | $ | $$$ | $ (but mostly wasted) |
| Winner for sleep? | ✅ | — | (brain-specific, not sedating) | ❌ |
Practical takeaway: for sleep, Glycinate. For chronic constipation, Citrate. For cognition (separate question), Threonate. Avoid Oxide for anything but cheap laxative effect.
Example — Fish oil brands compared for cardiovascular
Comparing three popular Omega-3s at 1 g EPA+DHA per day:
- Brand A (premium): Independently tested for oxidation, IFOS 5-star, ~$1.20/serving.
- Brand B (mid-tier): USP-verified, no public oxidation test, ~$0.60/serving.
- Brand C (cheap): No third-party testing, oxidation tests show rancidity in independent reviews. ~$0.30/serving.
The tool flags Brand C as a hard no — rancid fish oil is not just ineffective, it’s pro-inflammatory (the opposite of why you’re taking it). Brand B is the value pick. Brand A is the right call if you’re taking high doses (3+ g/day) or want maximum testing.
Quick-pick: which form for which goal
The fast lookup. If you only care about one thing, this table gets you to the right form in 10 seconds.
| If your goal is… | Best form | Why |
|---|---|---|
| Sleep / anxiety / relaxation | Magnesium Glycinate | Calm without GI effects; high bioavailability |
| Constipation | Magnesium Citrate | Draws water into the bowel; gentle laxative effect |
| Cognition / memory | Magnesium L-Threonate | Only form that crosses the blood-brain barrier well |
| Cheap, basic deficiency fix | Magnesium Glycinate (not Oxide) | Oxide is ~4% bioavailable; Glycinate is ~$3 more and 4–5× more usable |
| Iron deficiency (general) | Iron Bisglycinate | High absorption, low GI upset vs. ferrous sulfate |
| Iron deficiency (severe / under medical guidance) | Ferrous sulfate | Cheap and effective; tolerate the GI cost |
| Vitamin D supplementation | D3 (cholecalciferol) + K2 (MK-7) | D2 is 2–3× less effective; K2 routes Calcium correctly |
| Omega-3 (general health) | Fish oil — EPA+DHA combined, IFOS-tested | Form is less important than oxidation status |
| Omega-3 (vegan) | Algal oil DHA+EPA | The only complete vegan source; flax/chia don’t reliably convert |
| B12 (most people) | Methylcobalamin sublingual | More active; sublingual bypasses absorption issues |
| B12 (MTHFR mutation) | Methylcobalamin (not Cyanocobalamin) | Bypasses the broken methylation step |
| Creatine | Monohydrate | Cheapest form is also the most-studied. Anything else is marketing. |
| Curcumin | Curcumin + Piperine (or Meriva / phytosome) | Plain Curcumin is poorly absorbed; the additions raise bioavailability ~20× |
| CoQ10 (under 40, healthy) | Ubiquinone | Body converts it; cheaper |
| CoQ10 (over 40, on statins, or for fertility) | Ubiquinol | Pre-converted, better-absorbed at older ages |
Brand tier rules of thumb
When the form is right, brand mostly comes down to testing tier. Quick guide:
- Costco / Kirkland — surprising amount of third-party testing for the price. Best value tier for fish oil, multivitamins, basics.
- NOW Foods / Doctor’s Best / Nature’s Way — value-leaning quality. Long track records. No specialty forms but the basics are solid.
- Thorne / Pure Encapsulations / Designs for Health — practitioner-grade. NSF Certified for Sport options. Worth it for athletes, sensitive users, and 10+ supplement stacks.
- Klaire Labs / Seeking Health — niche / specialist (methylation support, sensitive populations).
- Anything Amazon-only with no website — skip.
FAQ
How do you decide which form "wins"?
Each comparison is goal-anchored. Magnesium for sleep, Citrate for constipation, Threonate for cognition — they're all "good" forms in their lane and not interchangeable. The winner is whichever form has the strongest evidence for the *specific goal* you selected.Is the cheapest option always bad?
No. For many supplements (Creatine Monohydrate, Vitamin D3, basic Magnesium Glycinate), the cheap version *is* the right version — the molecule is the molecule. The expensive option is worth it when (a) the form genuinely matters, or (b) third-party testing matters for your situation (athletes subject to drug testing, people with sensitivities, anyone stacking 10+ supplements).What's the difference between this and the Cost Calculator?
The Comparison Tool helps you **pick the right form/brand** for a single supplement. The Cost Calculator takes your final picks and prices out your whole monthly stack. Use Comparison first, then Cost Calculator.Why aren't all brands listed?
We only include brands that pass a curation filter: no FDA warning letters, no documented fake-review patterns, no repeated independent testing failures. That removes a lot of Amazon-only brands. If a brand you trust isn't listed, let us know via the contact page.Can I compare different supplements (not just different forms)?
For "X vs Y as a sleep aid" type questions (e.g., Magnesium vs Melatonin vs Ashwagandha), check the goal-specific guides in the Goals section — those compare across categories. This tool is built for in-category comparisons.Related
- Stack Analyzer — once you’ve picked forms, check the whole stack
- Cost Calculator — total your monthly cost across all picks
- Browse supplements — full database
- Browse comparisons — long-form head-to-head articles