Vitamin D and Perimenopause: Why So Many Midlife Women Are Deficient (and What to Do About It)

If you've spent the last decade dutifully slathering yourself in factor 50 the second the sun makes an appearance, this post might leave you scratching your head.

Because here's the thing - and it's the kind of thing nobody talks about at the school gates or in the GP's office - slapping on the sun-cream the minute the sun appears is leaving a sizable chunk of women in midlife walking around with sub-optimal Vitamin D levels.

In a 2025 study of 191 perimenopausal women, published in European Psychiatry, 78% had Vitamin D levels below the normal range. Seventy-eight percent.

So before we get into another sun-and-SPF season, I want to give you a more nuanced take on Vitamin D, sun exposure, and how low and sub-optimal levels can affect women’s moods, energy, bone and hormone health in perimenopause.

Vitamin D - Is it a Vitamin or Hormone?

Technically, Vitamin D is a hormone, which is important in (peri)menopause for:

• Bone density and muscle strength - Vitamin D is essential for calcium absorption, bone remodelling, and muscle function. This becomes especially important during perimenopause and menopause, when declining oestrogen accelerates bone loss and increases the risk of fractures.

• Mood regulation and emotional well-being - Low Vitamin D levels are associated with a higher risk of low mood and depressive symptoms, including in perimenopausal women. Adequate Vitamin D may help support overall brain and nervous system health alongside other lifestyle and hormonal factors.

• Immune regulation - Vitamin D helps regulate immune activity, supporting a more balanced and appropriately responsive immune system rather than an overly reactive one. This matters in midlife, when inflammatory and autoimmune conditions become more common in women.

• Hormone signalling and metabolic health - Vitamin D interacts with several hormone pathways, including oestrogen, insulin, and thyroid signalling. Adequate levels may support insulin sensitivity, mood, energy production, and overall metabolic health during perimenopause.

• Skin barrier and inflammatory skin health - Vitamin D plays a role in maintaining the skin barrier and regulating inflammation, which may be relevant for conditions such as eczema, psoriasis, acne, and increased skin sensitivity often experienced during hormonal shifts.

So if you've been noticing more fatigue, depressive periods, painful joints, skin breakouts, or (auto) immune issues, keep reading.

The Midlife Trap

Here's why women in their 40s and 50s are more vulnerable to Vitamin D deficiency than they were in their 30’s:

1. Skin synthesis slows with age. The skin's ability to make Vitamin D from sunlight reduces over time, so even the same amount of sun exposure produces less vitamin D as we get older.

2. Hormonal changes. Declining oestrogen during perimenopause and menopause appears to influence how Vitamin D is absorbed, activated, and used in the body, which may contribute to lower overall levels

3. Indoor lifestyles dominate. Most women work indoors, exercise indoors, and commute by car, bus or train, so their skin barely sees daylight.

4. SPF. Applying SPF under your makeup or the moment you step outside every day, year-round, to protect your skin from ageing may be making it almost impossible for your skin to produce any Vitamin D at all

Put those factors together, alongside living in northern climates and it’s easy to see why Vitamin D insufficiency is common in countries like Ireland, the UK and much of northern Europe.

Symptoms Of Low Vitamin D Most Women Miss

Low Vitamin D levels can show up as a vague collection of symptoms:

• Persistent low mood or low motivation

• Tiredness that doesn't lift after a good night's sleep

• Aching muscles or joints

• More colds, bugs, immune issues than usual

• Hair shedding

• Skin issues that just won't settle

So vague, Vitamin D can be easily overlooked, ignored or missed 

Safe Sun Exposure and Supplementation

Here's where the conversation around sun, SPF, and vitamin D gets nuanced, and where I want to play fair: dermatologists are right to be concerned about and educate about UV damage and skin cancer, and I don't ever want to dismiss that. But somewhere along the line, conversation about the importance of safe sun exposure and healthy vitamin D levels got left behind. 

A more balanced approach, supported by research on Vitamin D synthesis, looks like this:

Short, sensible exposure. My best advice is to speak to your dermatologist or skin specialist about how much sun you should get based on your skin type, age and climate. More generally, the recommendations are to aim for a pinking dose, around 10-20 minutes of sun exposure daily on the inside of bare arms and legs, during the months when UVB is strong enough where you live. Avoid redness and burning. 

Cover up after that. Once you've had your 10-20 minute dose, grab the SPF and hats, and head for the shade.

When to supplement. Vitamin D stores you build up in summer can carry you partway through winter, but for most of us in northern Europe, supplementation between October and March may be necessary. Talk to your GP about testing your levels in Autumn and again in spring so you can dose appropriately.

Food Sources Are Helpful, but Not Enough

Vitamin D-rich foods - oily fish, egg yolks, liver, fortified products - should be included in your diet, but in truth, they're rarely enough to maintain optimal levels, especially in midlife and especially in northern climates. Sunshine and, when needed, a good-quality supplement are usually necessary when it comes to maintaining healthy levels of vitamin D.

Three Things To Consider This Month

If you're heading into the summer months feeling a bit flat, foggy, or just not quite yourself, here’s what you can do: 

1. Get your Vitamin D tested to assess your baseline (especially if you haven't been tested recently, you haven't supplemented, or you have darker skin). Most GPs will do it once or twice a year; private testing is also widely available.

2. Build short, sensible sun exposure into your day. A 15-minute walk at key times with bare arms and legs will support Vitamin D synthesis without being reckless.

3. Pair it with smart protection. Have your SPF, hat, and cover-up ready for after that window, not as a default reflex the moment you step outside.

When Lifestyle Tweaks Aren't Enough

If you've been doing the right things and you still feel like something's off - your energy, mood, sleep, weight, or skin - it might be time to look deeper. Vitamin D in perimenopause is just one piece of a much bigger picture, and in midlife, that picture is rarely simple.

I work with women to map out what's actually going on beneath the surface, using functional testing and personalised nutrition to support hormones, energy, and metabolism at every stage of their hormone journey, including perimenopause and beyond.

If you'd like to chat about whether that approach could help you, let’s talk. You can book a free call here.

Frequently Asked Questions

How much sun do I need for Vitamin D?

For most light-skinned adults at northern latitudes, 10-20 minutes of midday sun on bare arms and legs, several times a week during late spring through early autumn, is usually enough to support healthy Vitamin D production. Darker skin tones need longer - often 25-40 minutes - and older skin synthesises less, so duration may need to be at the upper end. The key is exposure, short of any redness or burning.

Can low Vitamin D cause fatigue and low mood in perimenopause?

Research has linked low Vitamin D to both fatigue and depressive symptoms in perimenopausal women. While it's rarely the only factor, it's a common, easily-tested contributor that's worth ruling in or out before assuming symptoms are 'just hormones'.

Should I take a Vitamin D supplement?

For most women in northern Europe, some supplementation between October and March is sensible, and longer for those with darker skin, indoor lifestyles, or known deficiency. Dose depends on your starting level, which is why testing first matters. Speak to your GP or a qualified practitioner for personalised guidance.

Does sunscreen block Vitamin D production?

Yes - SPF 30, applied properly, can reduce Vitamin D synthesis in the skin by up to 95%. That's exactly what it's designed to do. The workaround isn't skipping SPF altogether, it's sequencing: a short, sensible exposure window first, then SPF for the rest of your time outside.

What's the best food source of Vitamin D?

Oily fish (salmon, mackerel, sardines), egg yolks, liver, and fortified foods are the main dietary sources. Helpful additions to your diet, but rarely enough on their own to maintain optimal levels - especially in midlife and especially in cloudier climates.

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This post is for general information and education and is not a substitute for individual medical advice. If you have concerns about your Vitamin D levels or any symptoms you're experiencing, please speak with your GP or a qualified healthcare practitioner.