Hair Loss After COVID or Weight-Loss Injections: What’s Behind It and How to Support Your Scalp
In short: If you suddenly lose noticeably more hair two to three months after a COVID infection, a feverish illness or rapid weight loss (for example with a weight-loss injection), the cause is usually telogen effluvium: many hair follicles switch into the resting phase at the same time and later shed together. It is distressing, but usually temporary. The cause should be checked by a doctor – and in the meantime you can care for and support your scalp in a targeted way.
What we see at MetaBeauty
Since 2020 we have been receiving more and more messages that sound very similar: “I had COVID, and three months later I was finding clumps of hair in my brush.” Over the past two years a second group has joined them: people who lost a lot of weight in a short time with so-called weight-loss injections (GLP-1 medicines such as semaglutide) or a strict diet – and then notice that their ponytail is getting thinner.
Both situations often share the same mechanism. That is why we explain here what happens in the hair cycle, when you need medical advice and which scalp care from our range we recommend – with study data instead of promises.
What is telogen effluvium?
Every hair goes through a cycle: a long growth phase (anagen, several years), a short transition phase (catagen) and a resting phase (telogen, about three months), at the end of which the hair falls out. Normally around 10–15 % of hairs are in the resting phase – which is why losing 50–100 hairs a day is normal.
A strong stressor for the body – high fever, an infection, surgery, a significant calorie deficit, severe stress – can push many follicles into the resting phase at once. Because this phase lasts about three months, the hair falls out with a delay: typically two to three months after the trigger. That is exactly why many people don’t connect the hair loss with the illness at first.
Typical signs of telogen effluvium:
- The shedding is diffuse, spread across the whole scalp – no bald, sharply defined patches.
- A striking amount of hair comes out when washing and brushing, often with a small light bulb at the root.
- The scalp otherwise looks healthy.
- Once the trigger is gone, shedding usually normalises within a few months; according to the American Academy of Dermatology, it often takes six to nine months for hair to regain its previous fullness.
Hair loss after COVID
Hair loss after COVID-19 is now well documented. Studies show that it occurs mainly after illness with fever and usually begins two to three months after the infection (overview in PMC). It can also happen after mild cases. Other factors from that time often add to it: stress, reduced appetite, poor sleep.
Hair loss after rapid weight loss and weight-loss injections
With rapid weight loss the body receives less energy, protein and micronutrients. Hair follicles are among the most active cells in the body – and react accordingly. This applies whether the weight loss comes from a diet, surgery or medication.
There is early data on GLP-1 medicines: a large analysis of insurance claims found a higher risk of hair loss in women on semaglutide than on another weight-loss medicine, but the authors describe the overall results as inconclusive (medRxiv, 2025). The rapid weight loss itself probably plays the biggest role.
Important: Do not stop a prescribed medicine on your own because of hair loss. Talk to your doctor – adjusting protein intake and checking iron and vitamin levels often already helps.
When to seek medical advice
- The increased shedding lasts longer than six months.
- Bald, sharply defined patches appear.
- The scalp is red, flakes heavily, itches, burns or hurts.
- The hair is thinning mainly at the parting, crown or temples – this may point to hereditary hair loss that becomes more visible through an effluvium.
- You also feel exhausted, get cold easily or have other symptoms.
A blood test (including ferritin/iron, thyroid, vitamin D, zinc) and a scalp examination by a dermatologist or in a trichology practice are then advisable.
What you can do yourself
- Eat enough protein – especially while losing weight.
- Be gentle: no tight hairstyles, little heat, don’t rub wet hair.
- Wash regularly: washing does not cause hair loss – the hairs that come out would have been released anyway.
- Track your progress: photos every four weeks from the same angle and in the same light.
- Care for your scalp in a targeted way – so it offers good conditions during the recovery phase.
The scalp care we recommend – and what the studies show
For phases of increased shedding we recommend DSD de Luxe products that have been tested in independent efficacy studies. Particularly relevant for telogen effluvium: two studies measured how the share of hairs in the resting phase (telogen) changes.
9.4 Aminopyrrole + Melatonin Lotion
In a study with 46 participants (aged 18–60), the number of shedding hairs fell by 31.71 % after 28 days and by 71.36 % after 56 days. The share of hairs in the resting phase decreased by 15.55 % after 58 days, and hair diameter increased by 2.71 %.
See the study and product →
3.1 Intense Shampoo + 3.4.1 Crexepil de Luxe Forte Lotion
In a study with 46 participants (aged 18–60) with hair loss, the combination reduced hair loss by 31.23 % and the share of hairs in the resting phase by 15.91 %. 96 % noticed less hair loss when washing.
See the study → · Study set 3.1 + 3.4.1 →
9.1 Exogrow Booster Shampoo + 9.4.1 Exogrow Booster Lotion
In a 56-day study with 21 adults with hair loss, 95 % noticed that their hair was falling out visibly less; according to the manufacturer, hair density increased by 19 %.
See the study and set →
As a base: 1.3 Peeling
A scalp peeling once or twice a week removes flakes and residue so that lotions reach the scalp better. In a 28-day study, 1.3 Peeling reduced keratin deposits on the scalp by 79 %.
See the study and product →
| Product | Study | Key result |
|---|---|---|
| 9.4 Aminopyrrole + Melatonin | 46 people, measured after 4 and 8 weeks | −71.36 % shedding hairs after 56 days |
| 3.1 + 3.4.1 Crexepil Forte | 46 people, approx. 10 weeks | −31.23 % hair loss, −15.91 % telogen share |
| 9.1 + 9.4.1 Exogrow | 21 people, 56 days | 95 % noticed less hair loss |
| 1.3 Peeling | 22 people, 28 days | −79 % keratin deposits |
To be honest: none of these studies was carried out specifically with people after COVID or after weight loss. The results refer to the respective study group; individual results may vary.
Frequently asked questions
Does hair grow back after COVID?
With telogen effluvium the hair follicles remain intact. In most cases the hair grows back; it often takes six to nine months to regain its previous fullness.
When does hair loss start after an infection or weight loss?
Usually two to three months after the trigger – that is how long the resting phase of the hair lasts.
Do weight-loss injections cause hair loss?
Hair loss is observed with GLP-1 medicines. Based on current knowledge it is mainly linked to rapid weight loss. The evidence is not yet conclusive. Do not stop medication on your own – discuss it with your doctor.
How long should I use a scalp treatment?
The studies above ran for four to twelve weeks. We recommend consistent use for at least eight weeks and documenting progress with photos.
Can I combine the products with medical treatment?
Cosmetic scalp care does not replace treatment but can complement it. If in doubt, ask your doctor.
Not sure which care suits your situation? Write to us – our trichology-trained team will be happy to advise you.
This article is for information only and does not replace a medical diagnosis or treatment. The products mentioned are cosmetics, not medicines.