There are at least 28 identified types of collagen in the human body. Five of them appear in supplements: Types I, II, III, V and X. Only three, I, II and III, have meaningful human evidence behind supplementation.
Type I alone makes up roughly 90% of the collagen in your body. That single fact resolves most of the confusion around this topic: a supplement supplying Type I is supplying the type you have most of, and the marketing value of additional types on a label runs well ahead of the evidence for them.
Here’s the complete reference.
The collagen types found in supplements
| Type | Where it occurs in the body | Structural class | Supplement source | Human supplement evidence |
|---|---|---|---|---|
| Type I | Skin, bone, tendon, ligament, teeth. ~90% of total body collagen | Fibrillar | Bovine hide, fish skin and scales, porcine | Strong for skin hydration and elasticity; moderate for bone and tendon |
| Type II | Cartilage, intervertebral discs, vitreous humour of the eye | Fibrillar | Chicken sternal cartilage | Moderate, but only for undenatured UC-II at ~40 mg, a different mechanism entirely |
| Type III | Skin, blood vessels, reticular fibres, internal organs. Usually alongside Type I | Fibrillar | Bovine hide | Limited as an isolated type; almost always studied together with Type I |
| Type V | Hair, cornea, placenta, cell surfaces. Regulates how Type I fibrils assemble | Fibrillar | Eggshell membrane | Insufficient, no supplementation trials |
| Type X | Hypertrophic cartilage during bone growth and fracture repair | Network-forming | Eggshell membrane | Insufficient, no supplementation trials |
| Type IV | Basement membranes, kidney filtration | Network-forming | Not available in supplements | Not applicable |
Types IV is included because it’s a major structural collagen people encounter in biology contexts. It doesn’t appear in supplements at all, which is worth knowing before you look for it.
Type I collagen: the one that matters most
Type I is the dominant collagen in the human body and the one with by far the strongest supplement evidence.
Where it occurs: skin, bone, tendon, ligament, dentin, and scar tissue. It’s the structural protein that gives these tissues tensile strength, gram for gram, Type I collagen fibres are comparable in tensile strength to steel.
Why it dominates supplements: it’s the most abundant type in the animals collagen is sourced from, so it’s what you get regardless of whether the source is bovine hide or fish skin. Marine collagen is roughly 90% or more Type I. Bovine collagen supplies Type I and III together.
Evidence: the strongest in the category. Randomised trials consistently show improvements in skin hydration and elasticity after 8–12 weeks of daily use. Bone density and tendon evidence is more modest but real.
If you’re buying collagen for skin, you’re buying Type I whether the label emphasises it or not.
Type II collagen: cartilage, and a critical distinction
Type II is the primary collagen in cartilage, and it’s the type most associated with joint health. It’s also the type where the biggest misunderstanding in the category lives.
There are two completely different ways Type II is used in supplements, and they are not interchangeable.
Undenatured Type II (UC-II) is used at roughly 40 mg per day. It works through an immune mechanism called oral tolerance, which depends on the collagen retaining its native three-dimensional structure. This is the form used in the joint trials people cite.
Hydrolyzed Type II has been broken into peptide fragments like any other collagen peptide. Hydrolysis destroys the structure oral tolerance requires, so hydrolyzed Type II does not inherit the UC-II evidence.
A multi-collagen blend advertising “Type II collagen” is almost always using the hydrolyzed form. The label is accurate; the implied benefit is not.
Full mechanism and dosing detail in type II collagen.
Type III collagen: the partner to Type I
Type III occurs throughout skin, blood vessels and internal organs, forming what are called reticular fibres. It’s more abundant in younger skin and in the early phases of wound healing, and it declines with age faster than Type I.
In practice, Type III is almost never sold or studied on its own. It comes bundled with Type I in bovine collagen at a ratio typically cited as around 90:10.
That bundling means there’s no clean evidence for Type III specifically. Trials on bovine collagen are trials on Types I and III together, and there’s no way to attribute the results to one or the other.
What this means practically: “contains Types I and III” is an accurate description of bovine collagen, not a distinguishing feature. Nearly all bovine collagen contains both.
Type V collagen: real biology, no supplement evidence
Type V is a genuine and important collagen. It occurs in hair, the cornea, placental tissue and on cell surfaces, and it plays a regulatory role, it helps control how Type I fibrils assemble and how thick they become. Mutations in Type V collagen cause classical Ehlers-Danlos syndrome, which gives some sense of how structurally significant it is.
None of that is evidence that supplementing it does anything.
Type V appears in supplements almost exclusively through eggshell membrane, in small quantities within a blend. There are no clinical trials testing whether supplemental Type V produces any measurable outcome.
The honest position: Type V on a label is a completeness claim. It isn’t harmful and it isn’t a reason to pay a premium.
Type X collagen: growth-plate biology, not a supplement target
Type X is a network-forming collagen found in hypertrophic cartilage, the zone where cartilage is being converted to bone during growth, and at fracture repair sites.
Its biological role is specific and time-limited. It’s a marker of a particular stage in bone formation rather than a general structural component of adult tissue.
Like Type V, it reaches supplements via eggshell membrane, in small quantities, with no supplementation trials behind it.
The honest position: same as Type V. Present on labels because it can be, not because it’s been shown to do anything.
What type of collagen is best for your goal
This is the question most people actually arrive with. The answer is more straightforward than the labelling suggests.
| Your goal | Type to look for | Practical recommendation |
|---|---|---|
| Skin hydration and elasticity | Type I | Any bovine or marine collagen at 5–10 g daily |
| Joint comfort | Type II (undenatured) | A dedicated UC-II product at ~40 mg, not a blend |
| Bone density | Type I | Bovine collagen; the notable trials used bovine peptides |
| Tendon and ligament | Type I | Bovine collagen, usually studied with vitamin C and loading exercise |
| Hair and nails | Type I | Modest evidence for nails, weak for hair |
| General wellbeing | Type I and III | Standard bovine collagen is fine and cheapest |
Two things fall out of this table.
Type I covers almost everything. For every goal with real evidence except joints, Type I is the answer, and Type I is what standard collagen supplements supply.
Joints are the one genuine exception, and the answer there isn’t a blend containing Type II, it’s a dedicated undenatured product at a much smaller dose, working through a different mechanism.
Why collagen type matters less than the label suggests
Here’s the point that reframes everything above, and it’s the one most product pages avoid.
Your body does not reassemble ingested collagen by type.
When you take collagen, it’s broken down in digestion. Most of it becomes free amino acids. A portion survives as small di- and tripeptides, particularly prolyl-hydroxyproline, which are absorbed intact and appear to act as signalling molecules prompting your own fibroblasts to increase collagen production.
Neither pathway preserves type identity. Eating Type V collagen does not route Type V collagen to your corneas. The peptides your body absorbs are raw material and signals; your cells decide what to build with them based on what your tissues need.
This is why the type count on a label is a weaker signal than it appears, and why “five types” doesn’t outperform “one type” at the same dose. The detail on how absorption actually works is in collagen peptides.
What genuinely differentiates products is dose, peptide profile, and third-party testing, not how many types appear on the front of the tub.
Where to buy each collagen type
- Type I and III (bovine), the default for most goals. Sports Research and Vital Proteins are the most widely stocked.
- Type I (marine), for pescatarians or those avoiding beef. See marine collagen.
- Type II (undenatured UC-II), a distinct product for joints, sold at ~40 mg. Not the same as Type II in a blend.
- Types V and X, only available inside multi-collagen blends via eggshell membrane. Not worth seeking out on their own.
Frequently Asked Questions
How many types of collagen are there?
At least 28 have been identified in the human body. Five appear in supplements, Types I, II, III, V and X, and only Types I, II and III have meaningful human evidence behind supplementation.
What is the most common type of collagen?
Type I, which accounts for roughly 90% of the collagen in the human body. It’s found in skin, bone, tendon and ligament, and it’s the type supplied by nearly all collagen supplements.
What is the difference between type 1 and type 3 collagen?
Both are fibrillar collagens found in skin. Type I provides tensile strength and dominates in bone and tendon; Type III forms finer reticular fibres and is more abundant in blood vessels and in younger skin. Bovine collagen supplies both together, so they’re rarely studied separately.
What type of collagen is best for skin?
Type I. It’s the dominant collagen in skin and the type with the strongest trial evidence for hydration and elasticity. Both bovine and marine collagen supply it.
What type of collagen is best for joints?
Undenatured Type II at around 40 mg, which works through an immune mechanism rather than by supplying building material. Hydrolyzed Type II in a multi-collagen blend is a different ingredient and doesn’t carry the same evidence.
Do I need all five types of collagen?
No. Your body doesn’t reassemble ingested collagen by type, so supplying more types doesn’t produce a broader effect. Dose and third-party testing matter considerably more than type count.
What is type 4 collagen and can I supplement it?
Type IV is a network-forming collagen found in basement membranes, including kidney filtration structures. It isn’t available in supplement form and isn’t included in multi-collagen blends.
Which collagen type declines fastest with age?
Type III appears to decline faster than Type I, which is one reason younger skin has a higher Type III proportion. Both decline steadily from around the mid-twenties.