What Does 25% IgG Mean? How to Read a Colostrum Label
Every colostrum brand wants you to look at its percentage. Almost none of them explain what the number actually means — or admit that a bigger percentage doesn't always mean more of what matters. Here is how to read a colostrum label like someone who works in the industry.
The IgG percentage tells you what proportion of the colostrum powder is immunoglobulin G — the antibody colostrum is prized for. But the number that actually matters is milligrams of IgG per serving: serving size × IgG %. A 2,300 mg serving standardized to 25% IgG delivers 575 mg of IgG. A “40%” product with a tiny 500 mg serving delivers only 200 mg. Always do the multiplication.
What is IgG, and why is it the number?
Immunoglobulin G — IgG — is the most abundant antibody in bovine colostrum and the primary reason adults supplement with it. IgG supports the immune system's surveillance work and helps maintain the integrity of the gut lining, which is where an estimated 70% of your immune activity lives.
Because IgG is colostrum's headline bioactive, serious manufacturers standardize their colostrum — meaning every batch is processed and tested to guarantee a consistent IgG concentration. A label that says “standardized to 25% IgG” is making a measurable, checkable promise. A label that just says “pure colostrum” is making no promise at all.
Percentage × serving = the real dose
Here is the calculation brands hope you'll skip. The IgG percentage only tells you the concentration. To know how much IgG you actually swallow, multiply it by the serving size:
- 2,300 mg serving × 25% = 575 mg IgG — this is the AURÔ Colostrum Powder label, exactly as printed on the Supplement Facts panel.
- 500 mg capsule × 40% = 200 mg IgG — a “higher percentage” product delivering nearly three times less IgG per serving.
- 1,000 mg serving × undisclosed % = ? — no percentage, no answer, no accountability.
This is why comparing colostrum products by percentage alone is like comparing coffees by roast color instead of caffeine. Concentration matters, but dose per serving is the truth.
| What the label says | What it tells you | What to do |
|---|---|---|
| “Standardized to X% IgG” + serving size in mg | Everything you need — concentration and dose are verifiable | Multiply and compare products honestly |
| IgG shown in mg per serving | The real dose, directly disclosed | Good sign — check for third-party testing next |
| High % on a tiny serving | Marketing math — concentrated but underdosed | Recalculate the actual mg before paying a premium |
| No IgG percentage at all | Nothing — the key ingredient is unverified | Assume the worst; choose a disclosed product |
Five things to check after the IgG
1. Serving size in milligrams. As above — the percentage is meaningless without it.
2. Sourcing. Grass-fed, pasture-raised herds produce colostrum the way nature designed it. “Grass-fed” on the label should be a sourcing commitment, not a decoration.
3. Calf-first collection. Ethical producers collect only the surplus after newborn calves have fed. It's a sign of a supply chain run with care rather than squeezed for volume.
4. Processing temperature. Immunoglobulins are fragile proteins. Low-heat processing preserves their activity; aggressive heat treatment can denature the very IgG you're paying for.
5. Third-party testing. Anyone can print a percentage. Independent laboratories verifying identity, IgG content, heavy metals and microbiology — batch by batch — is what separates a claim from a fact. This is the standard we hold ourselves to at the AURÔ laboratory page, where our testing philosophy is published.
A worked example, in full transparency
Take the AURÔ Colostrum Powder Supplement Facts panel. Per serving it reads: Bovine Colostrum (25% IgG) — 2,300 mg, delivering Immunoglobulin G — 575 mg. Grass-fed, from pasture-raised American herds, batch-tested by independent laboratories.
Every element of that sentence is checkable: the concentration (25%), the serving (2,300 mg), the resulting dose (575 mg IgG), the sourcing, and the verification. That is what a complete colostrum label looks like — from any brand. If a product you're considering discloses all five, it deserves your consideration. If it hides even one, you already have your answer.
Still weighing colostrum against other supplements? Our guide to colostrum vs collagen explains which does what — and when it makes sense to take both.
Colostrum you can verify
Standardized to 25% IgG · 575 mg IgG per serving · Grass-fed · Batch-tested.
Everything you want to know
Is a higher IgG percentage always better?
Not by itself. The percentage is a concentration, not a dose. A high percentage on a small serving can deliver less IgG than a moderate percentage on a full serving. Multiply percentage by serving size and compare the resulting milligrams of IgG.
What is a good amount of IgG per serving?
Quality adult colostrum supplements typically deliver several hundred milligrams of IgG per serving. AURÔ's powder provides 575 mg of IgG per 2,300 mg serving, standardized at 25%.
Why do some colostrum products not list an IgG percentage?
Usually because the product is not standardized — the IgG content varies batch to batch, or was never measured. Without a disclosed percentage or milligram amount, there is no way to verify what you are buying.
Does processing affect IgG content?
Yes. Immunoglobulins are heat-sensitive proteins. Low-heat, gentle processing helps preserve IgG activity, while aggressive heat treatment can denature it — which is why processing method belongs on your label checklist.
How can I verify a brand's IgG claim?
Look for third-party laboratory testing with published or available certificates of analysis. Independent verification, batch by batch, is the only way a percentage on a label becomes a fact rather than a claim.
This article is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Dietary supplements are not a substitute for a varied diet or medical advice. Consult a healthcare professional before starting any new supplement, especially if you are pregnant, nursing, or managing a health condition.
