If your hair sheds more in winter, there's a specific, fixable, deeply British reason that too few people connect the dots on: between roughly October and March, the sunlight in the UK is too weak for your body to make vitamin D at all. And low vitamin D is linked to hair shedding.
For a huge number of people, the winter hair shed and the winter vitamin D slump are the same story. Here's why, and what to actually do about it.
Why UK winters leave almost everyone short
Your skin makes vitamin D when exposed to UVB rays from sunlight. The problem is the angle of the sun. Through the UK winter, the sun sits too low in the sky for enough UVB to reach the ground, roughly from October to March depending on how far north you are. Scotland fares worse than Cornwall, but nowhere in Britain is making meaningful vitamin D from sunlight in January.
This is why UK health guidance recommends that adults consider a vitamin D supplement through the autumn and winter months. It's not a niche concern. It's close to a national default. Add in darker skin tones (which need more sun exposure to make the same amount), working indoors, and covering up against the cold, and winter deficiency becomes the norm rather than the exception.
How low vitamin D affects your hair
Vitamin D receptors are present in hair follicles, and vitamin D appears to play a role in the hair cycle, particularly in the process that moves follicles from their resting phase back into active growth. When levels run low, that cycling can be disrupted, and research has linked low vitamin D status to increased shedding and to certain types of hair loss.
The practical upshot: a winter dip in vitamin D can tip more of your follicles into shedding and make it harder for resting follicles to restart growth. Combine that with the natural autumn-to-winter seasonal shed, and you have two forces pushing in the same direction at the same time of year. It's little wonder the "why is my hair falling out in winter" searches spike every January.
The signs it might be a factor for you
Low vitamin D rarely announces itself dramatically, but common signs include persistent tiredness, low mood (it overlaps with the winter blues for a reason), aches, and more frequent minor illness, alongside the hair shedding. None of these is proof, which is exactly why testing matters.
What to actually do
This is where I want to be straight with you, because it's an area where supplement marketing often overreaches.
Get tested if you can. A simple blood test tells you your actual vitamin D level. Ask your GP, or use a reputable home finger-prick test. Knowing your number beats guessing, because both deficiency and excess matter.
Supplement sensibly through winter. UK guidance suggests many adults benefit from a vitamin D supplement in the autumn and winter. A common general maintenance dose is around 10 micrograms (400 IU) daily, though if you're found to be deficient your GP may advise more for a period. Don't megadose on a hunch: vitamin D is fat-soluble, it accumulates, and too much is genuinely harmful. This is one to get right rather than enthusiastic about.
Eat for it. Oily fish (salmon, mackerel, sardines), egg yolks, and fortified foods all contribute, though diet alone rarely covers a UK winter.
Catch what sun there is. On brighter winter days, time outdoors still helps your mood and general health even when UVB is too weak for vitamin D synthesis.
An honest word on what vitamin D won't fix
Here's the part that matters, and that a lot of brands blur.
Correcting low vitamin D can help with shedding that was driven or worsened by the deficiency. What it won't do is reverse hormonal hair thinning, because that has a completely different cause. If your hair loss is concentrated at your parting, temples or crown, comes back finer each cycle, and doesn't settle when spring returns, you're likely dealing with DHT-driven thinning, and no amount of vitamin D addresses that mechanism.
It's worth being clear that our Hair Growth Softgels are not a vitamin D product. They're formulated around saw palmetto (studied for its ability to help reduce DHT levels by up to 30%) and pumpkin seed oil (the subject of a 2014 clinical study in men, in which 400mg daily was linked to a 40% increase in hair count over 24 weeks), which target the hormonal mechanism, not the seasonal vitamin dip. So the sensible winter approach is often two separate jobs: fix the vitamin D through your GP, diet or a dedicated D supplement, and separately support the hormonal pathway if that's part of your picture.
The seasonal takeaway
In a UK winter, low vitamin D is close to universal, it's genuinely linked to shedding, and it's one of the most easily fixable factors behind that alarming January hair fall. Test if you can, supplement sensibly, eat well, and don't confuse it with hormonal thinning, which needs addressing on its own terms. Two problems, two solutions, and both worth sorting before spring.
(Vitamin D advice here is general; follow your GP's guidance for your own levels. Saw palmetto is not suitable during pregnancy or breastfeeding.)