Keratin

Structural protein forming the foundation of hair, nails, and skin, providing strength, elasticity, and protective barrier function

Scientific nameHydrolyzed keratin peptides FormulaVariable protein chains rich in cysteine Molecular weight10,000-50,000 Da g/mol CAS68238-35-7

85 absorption score

8 safety / 10

35 USD per month

5 documented interactions

Check it against something

Evidence level C

Keratin with:

75 out of 100

Works better together Compatible. Timing differs, so follow each supplement's own window.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Hair strength and damage repair

Directly repairs damaged hair cuticles and strengthens hair shaft

Keratin peptides fill gaps in damaged hair structure and reinforce protein matrix Evidence B-grade 2-6 weeks

Hair thickness and volume enhancement

Increases hair diameter and provides fuller, thicker appearance

Keratin deposits on hair shaft increasing thickness and structural integrity Evidence B-grade 4-8 weeks

Shine and smoothness improvement

Dramatically improves hair shine, smoothness, and manageability

Smooths hair cuticle and reduces friction for enhanced light reflection Evidence A-grade 1-4 weeks

Heat and chemical damage protection

Provides protective barrier against styling damage and chemical treatments

Forms protective protein layer reducing damage from heat and chemicals Evidence B-grade Immediate with cumulative benefits

Nail strength and flexibility

Strengthens nails while maintaining flexibility and reducing breakage

Reinforces nail keratin structure and improves protein cross-linking Evidence B-grade 4-8 weeks

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Creatine Monohydrate Strength & power enhancement 3-5g A 95% Calcium Bone health & muscle function 1,000-1,200 mg A 30% Magnesium Glycinate Superior absorption sleep & muscle support 200-600 mg A 90% Collagen Peptides Skin health & joint support 5-15g B 85% Bone Broth Collagen Gut healing & collagen support 20-40g powder B 85% Vitamin B7 (Biotin) Hair, skin & nail health 300-5000 mcg A 80%

Every pair we checked

12 combinations scored by the engine

Keratin + Caffeine No documented interaction either way No known interaction 70

Keratin + Creatine Monohydrate No documented interaction either way No known interaction 70

Keratin + Vitamin D3 No documented interaction either way No known interaction 70

Keratin + Calcium Carbonate No documented interaction either way No known interaction 70

Keratin + Whey Protein No documented interaction either way No known interaction 70

Keratin + Lactase No documented interaction either way No known interaction 70

Keratin + Bovine Collagen No documented interaction either way No known interaction 70

Keratin + DHA No documented interaction either way No known interaction 70

Keratin + Turmeric No documented interaction either way No known interaction 70

Keratin + Collagen Peptides Enhanced hair structure and growth support Works better together 75

Keratin + Vitamin B7 (Biotin) Comprehensive hair health and keratin synthesis Works better together 78

Keratin + NAC (N-Acetyl-L-Cysteine) Enhanced keratin strength and cross-linking Works better together 78

Dosage

Post shampoo

DailyTopical application

Hair repairApply 2-3 times weekly

MaintenanceApply 1-2 times weekly

Intensive treatmentApply daily for 1-2 weeks

Protective useApply before heat styling

When to expect it

First Effects1-2 weeks for immediate shine and smoothness improvements

Peak Benefits6-8 weeks for sustained strength and thickness benefits

Deficiency DevelopmentHair damage accumulates over time with styling and aging

Toxicity OnsetVery rare, mainly protein overload with excessive use

How to measure it

$80-150

MarkerHair analysis for protein content, amino acid profile

OptimalImproved hair protein structure, reduced damage markers

Deficient belowHigh hair porosity, protein deficiency markers

FrequencyEvery 6-12 months for hair health assessment

What people actually reported to the FDA

CAERS, 6 reports naming it as the suspect

Most reported effects

Swelling 2

Herpes virus infection 1

Lip swelling 1

Malaise 1

Oral herpes 1

Excluded from the list above: dysphagia (1). Those are people struggling with the tablet itself, not with the compound.

Named as the suspect 6 reports of 168 that mention it at all

Serious outcome 67% hospitalisation, emergency room or worse

Other Serious or Important Medical Event3

Visited Emergency Room2

Other Outcome2

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

Works better with

3 documented

Collagen Peptides

Enhanced hair structure and growth support

Both provide amino acids for hair protein synthesis · level C

Biotin

Comprehensive hair health and keratin synthesis

Biotin supports natural keratin production that supplements enhance · level B

Cysteine

Enhanced keratin strength and cross-linking

Cysteine provides sulfur for disulfide bond formation in keratin · level B

What not to take with Keratin

2 documented

Harsh Sulfates

Sulfate shampoos may strip keratin treatments

Strong detergents remove protein deposits from hair · moderate significance

Excessive Heat

High heat damages keratin structure

Heat breaks down protein bonds and structure · high significance

Medication interactions

Discuss these with a pharmacist before combining

no-major-interactions None

Generally safe with topical use

What to do: Safe external application

hair-chemical-treatments Minor

May interact with hair dyes or chemical treatments

What to do: Allow 48 hours between treatments

Available forms

bioavailability compared

Hydrolyzed Keratin Peptides (Low Molecular Weight) 85

Hydrolyzed Keratin Peptides (Low Molecular Weight): Direct hair repair, Immediate results, Visible improvements, Professional backing

Food sources

before you supplement

Hair-specific keratin supplements Hydrolyzed keratin peptides · 60

Wool keratin (dietary) Natural keratin protein · 40

Topical keratin treatments Direct hair application · 85

Keratin-rich hair masks Professional treatment products · 80

Too little

deficiency signs

Hair keratin damage and depletion:
Brittle, weak hair that breaks easily
Loss of hair shine and smoothness
Increased porosity and frizz
Split ends and structural damage
Reduced hair elasticity and flexibility
Dull, lifeless appearance

Too much

toxicity signs

Generally safe with some considerations:
Hair stiffness with protein overload
Scalp irritation in sensitive individuals
Product buildup with overuse
Temporary effects requiring consistent use

Who benefits most

damaged-chemically-treated-hair

Hair repair and reconstruction for chemically damaged or processed hair

Apply 2-3 times weekly

fine-thin-hair

Hair thickness and volume enhancement for fine or thinning hair

Apply 1-2 times weekly

heat-styling-damage

Protection and repair for heat-damaged hair from styling tools

Apply before heat styling + weekly treatment

aging-hair-changes

Age-related hair strength and structure support

Apply 2-3 times weekly

brittle-weak-nails

Nail strengthening and flexibility improvement

Apply daily to nails

Where to buy it

compare forms first

Look for Keratin at Topical application per serving. The form that matters here is Hydrolyzed Keratin Peptides (Low Molecular Weight).

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What else affects it

Beyond other supplements

Excessive heat

High heat damages keratin structure

Heat breaks down protein bonds and structure

How it works

Hydrolyzed keratin peptides penetrate hair cuticle and fill structural gaps
Forms temporary bonds with existing hair keratin reinforcing protein matrix
Smooths hair cuticle reducing friction and improving light reflection
Creates protective protein barrier against environmental and styling damage
Reinforces disulfide bonds in hair structure improving strength and elasticity
Provides amino acid building blocks for natural keratin synthesis

Key findings

what the evidence supports

Strong evidence for immediate hair smoothness and shine improvement
Good research on hair strength and damage repair benefits
Proven effectiveness for hair thickness and volume enhancement
Safe with proper use, protein overload possible with overuse

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Keratin?

Documented effects: Hair strength and damage repair; Hair thickness and volume enhancement; Shine and smoothness improvement; Heat and chemical damage protection. Directly repairs damaged hair cuticles and strengthens hair shaft

How much Keratin should you take per day?

The common daily range is Topical application. By goal — hair repair: Apply 2-3 times weekly; maintenance: Apply 1-2 times weekly; intensive treatment: Apply daily for 1-2 weeks; protective use: Apply before heat styling.

When is the best time to take Keratin?

Post shampoo. First effects are typically reported within 1-2 weeks for immediate shine and smoothness improvements.

What are the side effects of Keratin?

At excessive doses: Generally safe with some considerations:, Hair stiffness with protein overload, Scalp irritation in sensitive individuals, Product buildup with overuse, Temporary effects requiring consistent use. Safety rating at normal doses is 8 out of 10.

What should you not take with Keratin?

Separate it from Harsh Sulfates, Excessive Heat by two to four hours. Sulfate shampoos may strip keratin treatments

Does Keratin interact with medications?

Documented interactions with no-major-interactions, hair-chemical-treatments. Discuss these with a pharmacist before combining.

How do you know if you need Keratin?

The marker is Hair analysis for protein content, amino acid profile, optimal range Improved hair protein structure, reduced damage markers. Common deficiency signs: Hair keratin damage and depletion:, Brittle, weak hair that breaks easily, Loss of hair shine and smoothness, Increased porosity and frizz.

Taken for

31 Skin & Hair

Bovine Collagen · Marine Collagen · Collagen Peptides

43 Performance

Caffeine · Creatine Monohydrate · Whey Protein