Can Hair Regrow Naturally in 3 Weeks? What the Research Shows

We found no study showing that hair can regrow naturally in three weeks. The research on hair growth points the other way: hair follows a cycle with phases lasting long periods, shedding varies by season, and nutritional shedding can take many months to correct. Claims of three-week results shouldn't be trusted.

Here's what the research shows about timing.

I LOVE MY HAIR NOW

FullyVital hair serum and hair vitamins made tremendous improvements in my hair. I truly love my hair now.

Dorit S.,

Shop Hair Products

Key Takeaways

• We found no study showing natural hair regrowth in 3 weeks.
• A 15-year phototrichogram study of 10 men found alopecia involves a shorter growth phase for some hairs, finer hairs and longer gaps before regrowth.
• In 14 healthy men followed for 18 months, the share of scalp follicles in growth peaked in March at over 90% and was lowest in September, with shedding about 60 hairs a day in late summer.
• A review of nutritional hair loss in women said it can take many months to redress.

What Does Hair Regrowth Involve?

Each hair goes through a cycle. A hair that sheds has to enter a new growth phase, and a new hair has to grow long enough to be seen.

Is Three Weeks Realistic?

Not by the evidence we found. Studies of treatments and supplements measure results over months, not weeks.

Our Best Sellers

3-Month Growth Bundle

$269.00

Shop Hair System

Hair Revival Supplements

$47.20

Shop Vitamins

What To Do Instead

• Find the cause. A doctor can look at nutrition, health conditions and medicines.
• Expect months, not weeks, and track progress with photos.
• Be wary of fast-regrowth claims. We found no evidence for them.

Our Best Sellers

3-Month Growth Bundle

$269.00

Shop Hair System

Hair Revival Serum

$47.20

Shop Hair Serum

What The Research Shows

The Hair Cycle In Hair Loss

In a study that followed 10 men with or without alopecia by phototrichogram for 15 years, researchers accounted for almost 10,000 hair cycles. In alopecia, a growing proportion of hairs had a shorter growth phase, hair diameter declined, and the gap between a hair falling and regrowth beginning was longer. The authors said the shorter, finer hairs were absent more often and for longer periods (Courtois et al., 1994).

Seasonal Variation

Researchers measured hair growth every 28 days for 18 months in 14 healthy men. The proportion of scalp follicles in the growth phase reached a peak of over 90% in March and fell steadily to a trough in September, when shedding reached about 60 hairs a day, more than double the preceding winter's. The study shows that shedding can rise and fall through the year (Randall and Ebling, 1991).

Timing Of Nutritional Shedding

A review of nutrition and hair loss in women reported that in women the major cause of hair loss before age 50 is nutritional, affecting 30%, with persistent increased shedding as a principal change. The authors noted that correcting it can take many months (Rushton et al., 2002).

See also: Baby Hairs: Sign of Balding or New Regrowth? How to Tell the Difference · L-Lysine for Hair: What the Research Shows

For the bigger picture on what helps with thinning and shedding, see our guide to how to stop hair loss.

For how each stage of hair growth works and how fast hair grows back, see our guide to the hair growth cycle.

Frequently Asked Questions

Can hair regrow in 3 weeks?

We found no study showing it.

How long does hair regrowth take?

Studies of supplements and treatments measure over months. A doctor can tell you what to expect for your cause.

Why is my hair shedding more in some months?

One study found shedding peaked in late summer in healthy men.

References

1. Courtois M, Loussouarn G, Hourseau C, et al. Hair cycle and alopecia. Skin Pharmacol. 1994. PubMed
2. Randall VA, Ebling FJ. Seasonal changes in human hair growth. Br J Dermatol. 1991. PubMed
3. Rushton DH, Norris MJ, Dover R, et al. Causes of hair loss and the developments in hair rejuvenation. Int J Cosmet Sci. 2002. PubMed