Measuring Anagen Ratio and Shed Rate for Healthier Hair Growth

How do you know if shedding is normal or a sign of scalp imbalance?

Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a dermatologist or qualified healthcare provider for personalized care.

How do you tell if your hair is truly thinning or just cycling normally?

Hair naturally sheds every day as part of a healthy renewal cycle. However, for people with sensitive scalps or conditions like seborrheic dermatitis, telogen effluvium, or chronic inflammation, shedding can feel excessive or alarming. Distinguishing between normal shedding and early signs of thinning requires understanding measurable hair cycle metrics: anagen ratio (the percentage of actively growing hairs) and shed rate (the number of hairs lost over time). These metrics transform uncertainty into clarity, allowing both patients and clinicians to track scalp health objectively.

Learning how to measure these values can empower you to detect early changes in scalp balance, identify triggers, and evaluate whether treatments like topical therapies, nutritional support, or prescription medications are working. Once you understand the hair cycle’s rhythm, you can better interpret your scalp’s signals and approach hair changes with informed confidence.

What Is the Anagen Ratio?

The anagen ratio reflects how many hair follicles are currently in the anagen phase, or growth phase, compared to the total number of follicles. To understand why this number matters, it helps to know that the hair growth cycle occurs in three recurring stages:

1. Anagen (growth phase): The follicle is actively producing hair fiber. This stage can last anywhere from 2 to 7 years depending on genetics, hormones, and overall scalp health.

2. Catagen (transitional phase): A brief 2–3 week period where follicle activity slows, signaling the end of growth.

3. Telogen (resting and shedding phase): Lasting 2–3 months, this is when the old hair detaches and a new one begins forming beneath it.

In a healthy scalp, approximately 85–90% of hair follicles remain in the anagen phase¹, meaning most of your hair is actively growing. When chronic stress, nutrient deficiency, or scalp irritation disrupts this balance, more hairs prematurely enter the telogen phase, lowering the anagen ratio. The result can be diffuse thinning, increased shedding, or changes in scalp sensitivity.

Monitoring the anagen ratio offers insight into whether hair loss is due to temporary factors like illness or more persistent causes such as inflammation or hormonal imbalance.

How Is the Anagen Ratio Measured?

There are several techniques dermatologists use to assess the anagen ratio, each offering different levels of precision, comfort, and accessibility.

1. Trichogram (Microscopic Hair Analysis)

A trichogram involves gently plucking 50–100 hairs from various areas of the scalp and examining their roots under a microscope. The clinician classifies each root by its phase:

• Anagen bulbs are pigmented and elongated, indicating active growth.

• Catagen bulbs show early regression and partial pigmentation.

• Telogen bulbs appear small, round, and pale, representing resting hairs.

By calculating how many hairs fall into each category, clinicians can determine the ratio of growing versus resting hairs. For example, 88 anagen hairs out of 100 total correspond to an anagen ratio of 88%. A ratio below 80% can signal chronic telogen effluvium or early pattern hair loss.

Pros: Quantitative and well-documented in dermatological literature.
Cons: Slight discomfort due to hair plucking; requires professional handling.

2. Phototrichogram (Digital Scalp Imaging)

This advanced, non-invasive method captures high-resolution images of a defined scalp area to measure both hair density and growth rate. The process typically includes:

• Shaving a small patch of scalp (about 1 cm²).

• Taking baseline photographs.

• Re-imaging after 48–72 hours to identify hairs that have visibly lengthened; these are in the anagen phase².

The phototrichogram offers precise digital tracking over time, allowing doctors to visualize density changes, assess therapy response, and calculate growth rates in millimeters per day.

Pros: Painless, reproducible, ideal for monitoring progress.
Cons: Requires specialized imaging software and trained personnel.

3. Trichoscopy (Dermatoscopic Imaging)

Trichoscopy uses a dermatoscope, a magnifying tool equipped with polarized light, to visualize hair follicles and surrounding skin directly. It allows identification of characteristic features such as yellow dots (follicular openings with keratin), miniaturized hairs, or perifollicular scaling, which indicate the scalp’s condition.

Trichoscopy doesn’t measure the anagen ratio directly but helps detect disorders that alter it. Patterns like uneven follicle openings or reduced density can suggest a shift toward telogen dominance.

Pros: Quick, non-invasive, and rich in visual detail.
Cons: Requires expertise to interpret accurately; more qualitative than quantitative.

What Is Shed Rate and How Do You Measure It?

The shed rate measures how many hairs naturally fall from the scalp over a specific period. Because each follicle operates independently, shedding varies daily, but most people lose between 50 and 100 hairs per day³. A persistently higher count can indicate a disruption in the hair cycle, such as telogen effluvium, medication effects, or scalp inflammation.

1. Comb or Wash Test

This simple, repeatable home method involves counting hairs shed during washing or brushing:

• Avoid shampooing for three days.

• On day four, wash and condition your hair as usual.

• Collect shed hairs from the drain, towel, and comb, then count them.

Repeating this test weekly builds a personal baseline. If your shed rate doubles or remains elevated for several weeks, it may signal underlying stress, thyroid imbalance, or scalp sensitivity needing medical attention.

2. 60-Second Hair Count

Clinically validated, this method involves combing your hair forward for 60 seconds over a light surface and counting the hairs collected⁴. It’s best done at the same time each week for consistency. Tracking these numbers can reveal subtle trends, helping clinicians evaluate treatment response or flare-ups.

Tip: Perform this test on non-wash days to avoid counting loose, wash-related hairs twice.

3. Shedding Diary or App Tracking

Digital tools can complement manual methods. Many dermatology apps let users upload photos, log stress events, and record shedding counts. Over time, patterns emerge linking shedding spikes to triggers such as new products, illness, or hormonal fluctuations.

What Do These Metrics Reveal About Scalp Health?

A low anagen ratio or a high shed rate can point toward several underlying scalp or systemic imbalances:

• Inflammation: Chronic scalp conditions like seborrheic dermatitis can shorten the anagen phase.

• Nutritional deficiencies: Low iron, vitamin D, or zinc reduce follicle energy production and prolong telogen.

• Hormonal shifts: Thyroid disorders or elevated androgens can accelerate follicular miniaturization.

• Stress and illness: Physical or emotional stress can trigger temporary telogen effluvium.

Together, anagen ratio and shed rate provide a comprehensive picture of hair cycle behavior. Dermatologists use them to confirm diagnoses, adjust therapies, and track progress. For example, after starting anti-inflammatory scalp treatments or growth stimulants like minoxidil, a rising anagen ratio over several months signals regeneration and restored follicle stability.

When to Seek Professional Evaluation

If shedding feels excessive, hair texture changes, or the scalp becomes itchy, painful, or inflamed, schedule an appointment with a dermatologist or trichologist. Bring detailed notes and visuals:

• Recent photos showing the part line and temples.

• Hair care routines and any recent product changes.

• Diet, stress levels, and medications.

A clinician can perform a phototrichogram or trichoscopy, confirm whether your shedding is within a normal range, and recommend targeted care. Early professional evaluation is key; intervening before visible thinning begins yields the best outcomes.

Gentle At-Home Practices to Support Healthy Ratios

Even before seeing a specialist, consistent scalp care can improve comfort and reduce inflammation:

1. Choose mild, fragrance-free shampoos to avoid irritating sensitive skin.

2. Massage the scalp gently for a few minutes, several times per week, to stimulate blood flow.

3. Avoid tight hairstyles or heat styling that strains follicles.

4. Limit chemical processing such as bleaching or straightening.

5. Eat a nutrient-rich diet with adequate protein, omega-3s, and micronutrients.

6. Manage stress through mindfulness, yoga, or regular exercise, as cortisol can influence hair shedding.

Tip: Photograph the same scalp area every three months under consistent lighting. Subtle density increases are more visible in time-lapse comparisons.

Key Takeaway

Understanding and measuring the anagen ratio and shed rate transforms subjective worry into measurable insight. These metrics highlight whether hair is cycling normally or signaling underlying scalp stress. With compassionate care, consistent monitoring, and professional support, most people can regain balance and confidence in their scalp health.

Glossary

• Anagen: The active hair growth phase lasting several years.

• Catagen: Transitional phase marking the end of active growth.

• Telogen: Resting and shedding phase before regrowth.

• Trichogram: Microscopic hair analysis used to classify growth stages.

• Phototrichogram: Digital imaging technique to measure growth and density.

• Trichoscopy: Dermatoscopic imaging of scalp and follicles.

• Telogen Effluvium: Temporary hair shedding triggered by stress or inflammation.

• Miniaturization: Thinning of hair shafts due to follicle shrinkage.

• Perifollicular Inflammation: Localized immune reaction around hair follicles.

• Dermatoscope: Magnifying tool for scalp imaging.

Claims Registry

#	Claim	Source	Accessed (ET)	Anchor Extract	Notes
1	In healthy scalps, 85–90% of hairs are in anagen phase.	Harrison and Sinclair, British Journal of Dermatology, 2002	2025-11-07	"Normally 85-90% of scalp hairs are in anagen phase."	Peer-reviewed dermatology reference.
2	Phototrichogram measures hair growth by re-imaging after 48–72 hours.	Hoffmann, Skin Research and Technology, 2016	2025-11-07	"Hair growth assessment by phototrichogram uses 2–3 day intervals."	Clinical imaging standard.
3	Average daily hair shedding is 50–100 hairs.	American Academy of Dermatology Association, 2023	2025-11-07	"It’s normal to lose between 50 and 100 hairs a day."	Authoritative professional body.
4	60-second hair count is a validated method to assess hair shedding.	Shrivastava et al., International Journal of Trichology, 2010	2025-11-07	"The 60-second hair count is a simple, validated, and reproducible method."	Peer-reviewed clinical validation.