Types of Collagen Explained: Type I, II and III

Pick up a collagen supplement and you will often see "Type I", "Type I & III" or "Type II" printed on the label. Some products even list five types. It looks scientific, but what do these numbers actually mean? And should they decide which product you buy?

This guide explains the main types of collagen : where each one lives in your body, what it does and how that connects to the supplement aisle. 

Why Does Collagen Come in Different Types?

Collagen is not one single substance. Think of it as a family of proteins that share a family trait: a strong, rope-like shape built from three twisted chains. Each family member is made from slightly different chains, which changes how it behaves.

Scientists have identified at least 28 types, numbered with Roman numerals in the order they were discovered. That order says nothing about importance. Most of the collagen in your body comes from just a few of them, and three are worth getting to know.

Type I Collagen: The Body's Main Building Cable

Type I is the most plentiful collagen in the body. Its fibres are thick, tough and resist pulling, a bit like steel cables in a bridge.

Where you find it: skin, bones, tendons, ligaments and teeth.

What it does: it gives these tissues their strength. In bone, it forms the flexible framework that minerals such as calcium settle into. In tendons and ligaments, it lets tissue take strain without snapping.

Because Type I turns up almost everywhere in the body's structure, it is the type most often mentioned in skin and general wellness products.

Type II Collagen: The Cartilage Specialist

Type II is the main collagen in cartilage, the smooth, springy tissue that covers the ends of bones in your joints. It is also found in the nose, in the discs between spinal bones and in the gel-like part of the eye.

What it does: its finer, more loosely woven network traps water and creates a cushion. Think of it less like a cable and more like a firm sponge that absorbs pressure when you walk, climb stairs or bend your knees.

Because it is concentrated in cartilage, Type II is the type linked with joint-focused products.

Type III Collagen: The Flexible Support Layer

Type III builds finer, more flexible fibres. It often sits alongside Type I, adding stretch to tissues that need to give a little.

Where you find it: skin, the walls of blood vessels, and organs such as the intestines, liver and spleen. It is especially active in young skin and in the early stages of wound healing, when the body lays down a quick, flexible first repair before Type I takes over.

Type III gets less attention than Type I, but without it soft tissues would lose much of their flexibility.

Other Types You May Come Across

• Type IV does not form fibres. It forms thin, mesh-like sheets called basement membranes, which sit under skin and wrap around organs such as the kidneys.

• Type V is usually found together with Type I, helping to shape its fibres.

• Type X appears in the growing ends of bones in children and teenagers.

You will not often see these on supplement labels, but they show how specialised collagen can be.

Does the Type on the Label Tell You What a Supplement Will Do?

This is the question most articles skip, and it matters most.

It seems logical: Type I is in skin, so a Type I supplement should go to your skin. But your body does not work like a delivery service. When you swallow most collagen supplements, your digestive system breaks the protein into amino acids and short chains called peptides, just as it does with any protein. Your body then decides where to use them. A Type I label tells you which animal tissue the collagen came from, not where in your body it will end up.

So the type is useful information, but it is not a map. Research on collagen supplements, looks at specific products and specific outcomes, such as skin hydration or knee pain. A result from one product cannot simply be applied to every product with the same type number.

Hydrolysed vs Undenatured: The Label Detail That Matters More

There is one exception to the "digestion breaks everything down" rule, and it involves Type II.

• Hydrolysed collagen (collagen peptides) has already been broken into small pieces. This is the most common form, and most skin and joint studies use it. It is usually taken in grams per day.

• Undenatured Type II collagen is processed gently so the protein keeps its original shape. It is typically made from chicken breastbone cartilage. Researchers propose that it works differently, by interacting with the immune system in the gut rather than supplying building blocks. It is taken in tiny amounts, often milligrams rather than grams.

The two forms are studied separately, and evidence for one cannot be borrowed for the other. A review of eight trials of undenatured Type II collagen in early knee osteoarthritis reported better pain and function scores than placebo, but the authors noted the research is still limited. Neither form is a proven cure for joint problems.

Because the doses are so different, you cannot compare a "40 mg" label with a "10 g" label as if they measure the same thing. Always check which form the product contains.

Collagen Type vs Collagen Source

People often mix these up, so here is the difference. The type is the kind of collagen protein (I, II, III). The source is the animal it comes from. The two are linked, because different tissues contain different types.

These are common patterns, not strict rules, since the exact composition depends on the raw material and how it is processed. Check the product label or the manufacturer's documentation.

What About "Multi-Collagen" Products?

Some products combine several sources to list Types I, II, III, V and X together. Others add vitamin C or other ingredients. A longer list of types is not automatically better. What matters is the form of collagen, the amount per serving, the source, the other ingredients and the evidence for what the product claims to do.

Can I Choose a Type by Goal?

A sensible way to use this information is as a starting point for reading labels, not as a shortcut to results.

• If you are interested in skin or general wellness, you will mostly see Type I or Type I and III products, usually hydrolysed.

• If you are interested in joint comfort, you will see Type II products, either undenatured or hydrolysed. Check which, and see a doctor if joint pain, swelling or stiffness is ongoing.

• If you simply want to support your body's collagen, remember that your body makes its own from protein and vitamin C. 

Frequently Asked Questions

How many types of collagen are there?

 At least 28 have been identified, but Types I, II and III are the ones most people come across.

Which type of collagen is most common in the body?

Type I. It makes up most of the collagen in skin, bone, tendons and ligaments.

Is Type I or Type III better for skin?

Both occur naturally in skin and work as a team, so neither is simply "better". Supplement results depend on the product and the study, not the type number alone.

Is marine collagen Type I?

Marine collagen is mainly Type I, but check the product details to be sure.

Is Type II collagen only for joints?

It is mainly found in cartilage, which is why it is linked with joints. It also appears in spinal discs and the eye.

Do I need Types I, II and III together?

 There is no evidence that you must take every type. Whether a blend suits you depends on your goals, health and the product itself. A doctor or dietitian can help you decide.

Are there collagen types suitable for vegetarians?

All collagen supplements come from animals, so none are vegetarian or vegan. Plant-based diets can still supply the protein and vitamin C your body uses to make its own collagen.

Key Takeaways

• Collagen is a family of at least 28 proteins. Types I, II and III are the most familiar.

• Type I gives strength to skin, bone and tendons. Type II cushions cartilage. Type III adds flexibility to skin, blood vessels and organs.

• The type on a label shows what the collagen is made from. It does not predict where it goes in your body or what results you will see.

• Hydrolysed collagen and undenatured Type II collagen are different forms with different amounts and separate evidence.

• Check the source, form, serving size and allergen information before choosing any product.

Health Precautions and Disclaimer

This article is for general information and education only. It is not medical advice and is not intended to diagnose, treat, cure or prevent any disease.