The time it takes for hair to grow back after being lost depends on various factors, including the cause of hair loss, the individual's health, age, genetics, and hair care practices. Here are some general timelines based on different scenarios:

1. Normal Hair Growth Cycle:

   • Hair grows about 0.5 inches (1.25 cm) per month or around 6 inches (15 cm) per year.

2. Post-Pregnancy Hair Loss:

   • Many women experience hair loss postpartum due to hormonal changes. Hair typically starts to regrow within a few months, and most women see their hair return to its normal fullness within a year.

3. Telogen Effluvium:

   • This condition, often triggered by stress, illness, or other factors, causes temporary hair shedding. Hair usually starts to regrow within 3-6 months after the triggering event and can take up to a year to return to normal.

4. Alopecia Areata:

   • This autoimmune disorder causes patchy hair loss. Hair may regrow spontaneously within several months, though it can vary widely among individuals. Some people may experience complete regrowth, while others may have recurrent episodes.

5. Androgenetic Alopecia (Male or Female Pattern Baldness):

   • Hair loss from this genetic condition is typically progressive. Treatments like minoxidil or finasteride can help regrow hair or slow hair loss, but the timeline varies. Noticeable regrowth may take 3-6 months or longer.

6. Chemotherapy-Induced Hair Loss:

   • Hair typically starts to regrow 3-6 months after the end of chemotherapy, though the texture and colour may change temporarily.

7. Nutritional Deficiencies:

   • If hair loss is due to a deficiency (e.g., iron, biotin, zinc), addressing the deficiency can lead to regrowth within several months once proper nutrition is restored.

8. Scalp Conditions:

   • Conditions like fungal infections or psoriasis can cause hair loss. Effective treatment of the underlying condition can lead to hair regrowth within months.

Each person's situation is unique, so these timelines are general estimates. Consulting with a healthcare provider or dermatologist is recommended for personalized advice and treatment options.