Hair loss is not a diagnosis in itself - it is a symptom. Many different things can drive it, and very often they combine: stress stacks on top of an iron deficiency, which stacks on top of a recent illness. That is why a single “magic pill” rarely solves the problem. Here are the seven causes seen most frequently.
1. Stress and poor sleep
Prolonged emotional strain, anxiety, low mood and chronic sleep deprivation all affect the hair growth cycle. A share of follicles shift prematurely into a resting phase, and a few weeks later you notice increased shedding. The good news: this kind of shedding is often reversible once the stress eases.
2. Illness and surgery
A high fever, flu, COVID-19, operations and anaesthesia can all trigger shedding - not immediately, but two to three months after the event. That delay is what confuses people: the illness is long forgotten, yet the hair “remembers.” This pattern is called telogen effluvium - a delayed shed that usually recovers on its own.
3. Iron, protein and vitamin deficiencies
Hair is not a vital organ, so the body economises on it first. Low iron (especially low ferritin, your body’s iron reserves), insufficient protein, low vitamin D and certain B vitamins are common and entirely correctable causes. But taking supplements “just in case” is a mistake: you need to see the blood work first.
4. Hormonal changes
Thyroid dysfunction, pregnancy and the postpartum period, menopause, shifts in sex hormones and adolescence all affect hair. Postpartum shedding, for instance, is a typical and usually temporary story, whereas a thyroid problem needs treatment in its own right.
5. Chronic conditions
Chronic illness - especially of the gastrointestinal tract (which impairs nutrient absorption), as well as autoimmune and chronic inflammatory conditions - also shows up in the hair. Here shedding is a signal about your overall health rather than a standalone problem.
6. Rapid weight loss and some medications
Crash diets and fast weight loss are stress and deficiency at the same time, and hair responds predictably. Shedding can also be a side effect of certain medications or the result of unsupervised supplement use. If shedding started around a new medication, tell your doctor.
7. Androgenetic alopecia
This is a separate and very common cause, and its mechanism is different. The problem is less about how much hair sheds and more about the gradual miniaturisation of the follicles: hair becomes finer and weaker. Androgenetic alopecia progresses slowly, so the earlier it is caught, the more options there are to stabilise it.
What to do next
If shedding lasts longer than 2-3 months or is clearly getting worse, book a consultation. A trichologist performs trichoscopy, asks about the past few months (illness, stress, dietary changes) and orders blood work if needed. The goal is not to guess the cause but to see it.
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Frequently asked questions
- How long after stress or illness does hair fall out?
- Usually 2-3 months later. That delay is the hallmark of telogen effluvium: the trigger (illness, surgery, major stress) is already behind you, and the hair reacts with a lag. This is exactly why the cause is not always easy to connect to the effect.
- What blood tests are done for hair loss?
- The panel is tailored to you, but it often includes ferritin (iron stores), a full blood count, vitamin D, thyroid markers, and sex hormones where relevant. Ordering “everything” without an examination is not the way to go: the scope depends on your history and trichoscopy findings.
- Will vitamins help with hair loss?
- Only if there is a real deficiency they correct. With no deficiency, supplements will not speed up growth, and an excess of some nutrients is actually harmful. So the logical order is: blood work first, then targeted correction of what is genuinely lacking.
- Is hair loss after childbirth normal?
- Yes - postpartum shedding is common and usually temporary, driven by the change in hormone levels. It most often settles on its own within a few months. If it is very intense or drags on, see a doctor to rule out, for example, iron deficiency or a thyroid issue.
This article is for information only and does not replace a medical consultation. Decisions about your health need an individual assessment.
