Quick answer: Trichologists recommend finding the cause of thinning hair before treating it, usually with a scalp assessment and blood tests for things like iron, thyroid and vitamin D. After that, the basics matter most: a healthy scalp, enough protein, less tension and heat, patience, and proven treatments like minoxidil or in-clinic options where they suit you.
At Tess Hair and Scalp Clinic in Belfast, thinning hair is one of the most common things people come in about. And the first thing many of them tell me is how much rosemary oil they've already tried.
No judgement. Rosemary oil has had a better publicist than most celebrities. But it's not where a trichologist would start.
1. Find out why your hair is thinning
This is the one everyone skips, and it's the most important. Thinning hair has lots of possible causes, and they need different fixes:
shedding after illness, stress, surgery, a crash diet or having a baby
pattern thinning, which often runs in families
low iron, thyroid problems or low vitamin D
tension from tight hairstyles
breakage from heat, bleach or chemical treatments
scalp problems that make it a hostile place to grow hair
A trichologist works out which one (or which combination) you've got. Treating the wrong cause is like watering a plant that's actually missing sunlight. Very hydrated, still sad.
2. Get the right blood tests
Low iron stores, an underactive or overactive thyroid and low vitamin D can all contribute to thinning. Ask your GP about blood tests, or get them done privately, and bring the results to your trichologist.
One tip people rarely hear: if you take biotin supplements, tell whoever takes your blood. Biotin can affect some blood test results.
3. Treat your scalp like the soil it is
Hair grows from your scalp, so a red, itchy, flaky or congested scalp isn't doing your hair any favours. Wash often enough to keep it clean (yes, even if you've heard washing less is "better"), treat dandruff properly, and don't scratch it with your nails or a comb like it owes you money.
If your scalp has been unhappy for weeks, that's worth a proper look. We do scalp treatments for exactly this.
4. Eat enough protein, and don't crash diet
Hair is made mostly of a protein called keratin, and your body treats hair as optional when it's short of fuel. Crash diets and very low protein intake are classic triggers for shedding a couple of months later.
You don't need a special "hair diet". You need regular, proper meals with enough protein in them. (Sorry. I know "eat lunch" isn't as exciting as a £40 gummy.)
5. Be patient, because hair is slow
Hair grows in cycles that take months, so anything you change today won't show for a while. Most treatments need at least three to six months before you can fairly judge them.
This is where rosemary oil fans usually give up after a fortnight. (Rosemary oil is not the problem. The fortnight is the problem.)
Take a photo of your parting or hairline in the same light once a month. It's the most honest progress tracker you'll ever own.
6. Go easy on tension and heat
Tight ponytails, buns, braids, weaves and clip-ins can all pull on the follicles, especially at the hairline. Straighteners and bleach can weaken the hair until it snaps. Thinning edges in particular often recover if the tension stops early enough.
You don't have to give up styling. Loosen things up and rotate your styles. Your hairline deserves days off, because it's been working very hard.
7. Ask about minoxidil
Minoxidil is one of the best-studied treatments for pattern thinning, and you can buy it from UK pharmacies without a prescription. A few honest things to know first:
it takes months to see whether it's working
it can cause a temporary shed when you start
it only works while you keep using it
it isn't suitable for everyone, including during pregnancy or breastfeeding
Speak to a pharmacist or your GP before you start. The NHS hair loss treatments page is a good, plain summary.
8. Consider in-clinic treatments, honestly
Treatments like laser therapy, microneedling and PRP can help some people with some types of thinning. Results vary from person to person, and none of them are magic.
A good trichologist will tell you whether you're likely to benefit before you spend anything, and will say no when the answer is no. If you'd like that honest conversation, book a hair and scalp analysis first.
9. Look after your stress and sleep (as much as life allows)
A big stressful event can trigger heavy shedding a couple of months later. We're not going to tell you to "just relax", because nobody in history has ever relaxed on command. But sleep, regular meals and anything that takes the edge off do help your body (and your hair) recover.
10. Use your hairdresser while you wait
A clever cut, the right colour, volumising styling or a well-fitted topper can make thinning hair look fuller today, while the real work happens underneath. At Tess, the salon and the trichology clinic are under one roof, so you can sort the cause and the look in the same visit.
Rosemary oil, meanwhile, can stay in the cupboard as a lovely-smelling optional extra.
Frequently asked questions
Does rosemary oil work for thinning hair?
The evidence for rosemary oil is limited. If you like it and it doesn't irritate your scalp, it's unlikely to do harm, but it shouldn't delay getting the cause of your thinning checked.
Can thinning hair grow back?
Often, yes, depending on the cause. Shedding after illness or stress usually recovers. Traction thinning can recover if caught early. Pattern thinning can often be slowed or improved with treatment.
How long does it take to see results from a hair loss treatment?
Usually three to six months, because hair grows slowly and in cycles. Judging a treatment after two weeks isn't fair to the treatment.
What vitamins do trichologists recommend for thinning hair?
Only the ones you're actually low in. Blood tests can show whether you're short of iron, vitamin D or other nutrients. Supplements rarely help if your levels are already normal.
Does stress cause thinning hair?
A stressful event can trigger a type of shedding called telogen effluvium, usually a couple of months later. It's normally temporary.
Stop guessing, start fixing
Book a hair and scalp analysis at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast, or call 028 9096 4731. Bring your blood test results and your questions. Bring the rosemary oil too, if you must. See our treatments and prices.
About the author: Theresa Anthony is the trichologist at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast BT7 1JL, where hair loss treatment and a full hair salon sit under one roof.
The next step
Concerned about your hair or scalp?
A clinical consultation identifies the root cause rather than guessing at it — and gives you a written report and a plan.
