Vitamin D Deficiency in Perimenopause: A Complete Guide
Vitamin D deficiency is widespread in midlife women and worsens bone loss, mood, and fatigue. Here is what to know and how to address it.
Why Vitamin D Is Critical in Perimenopause
Vitamin D is technically a hormone precursor, and it influences far more in the body than bone health alone. It supports immune function, muscle strength, mood regulation, and the absorption of calcium. During perimenopause, falling oestrogen levels accelerate bone density loss, and vitamin D deficiency makes this significantly worse by impairing the body's ability to use the calcium it takes in. Low vitamin D has also been linked to low mood, fatigue, poor sleep, and increased susceptibility to infection, all of which can compound perimenopausal symptoms that are already challenging to manage.
How Common Is Deficiency and Who Is Most at Risk
Vitamin D deficiency is widespread. In the UK and many northern countries, it affects an estimated one in five adults. Skin makes vitamin D when exposed to UVB sunlight, but from October to March in the UK and similar latitudes, the sun angle is too low for this to happen effectively. People with darker skin need longer sun exposure to produce the same amount of vitamin D as those with lighter skin, increasing deficiency risk year-round. Other risk factors include spending most of the day indoors, wearing full-coverage clothing, being overweight (as vitamin D is stored in fat tissue and becomes less available), and having a diet low in fatty fish and eggs.
Vitamin D and Bone Health
Bone density typically peaks in the late twenties and then gradually declines. Oestrogen plays a protective role in slowing that decline, which is why perimenopause, with its fluctuating and falling oestrogen, is a critical period for bone health. Vitamin D works alongside calcium and other minerals to support bone mineralisation. Without adequate vitamin D, even a high calcium intake has limited benefit. Severe long-term deficiency leads to osteomalacia in adults, a softening of the bones that causes pain and weakness. More commonly, insufficiency simply accelerates the bone density loss that perimenopause already triggers.
Vitamin D and Mood
Vitamin D receptors are found throughout the brain, and deficiency has been consistently associated with low mood, depression, and seasonal affective disorder. During perimenopause, when mood fluctuations are already common due to hormonal changes, low vitamin D can deepen and prolong difficult periods emotionally. Some research suggests that correcting deficiency improves mood outcomes, though results across studies are mixed. What is clear is that optimising vitamin D levels removes one potential contributor to low mood, which is a reasonable step to take regardless of whether it turns out to be the primary cause.
Getting Enough Through Sun and Food
The body can produce substantial amounts of vitamin D from short daily sun exposure between April and September in the UK. Around 10 to 15 minutes of midday sun on the face, arms, and legs is enough for many people with lighter skin. Sunscreen limits production, so the recommendation is brief unprotected exposure followed by sunscreen for longer time outdoors. Food sources are limited but worthwhile. Oily fish such as salmon, mackerel, herring, and sardines are the best dietary sources. Eggs, particularly from pasture-raised hens, contain some vitamin D, as do fortified foods including some plant milks and cereals.
Should You Supplement and What Dose
Public health guidelines in the UK recommend that all adults consider taking 10 micrograms (400 IU) of vitamin D daily from October through March, and that those at higher risk take it year-round. For women with confirmed deficiency, therapeutic doses prescribed by a GP are typically higher, often in the range of 1,000 to 4,000 IU daily, sometimes more in the short term. Vitamin D3, the form produced by the skin, is more effective at raising blood levels than D2. Taking vitamin D with a meal containing some fat improves absorption, as it is a fat-soluble vitamin. Getting your level tested before supplementing helps you know where you are starting from.
Testing and Tracking Your Progress
A 25-hydroxyvitamin D blood test, available through your GP or privately, gives your current level in nanomoles per litre. A result below 25 nmol/L is considered deficient, between 25 and 50 is insufficient, and above 50 is generally considered adequate, with many specialists aiming for 75 to 100 nmol/L as optimal. Retesting after three months of supplementation confirms whether your dose is working. If fatigue, low mood, or bone-related pain are among your perimenopausal symptoms, tracking them over time alongside any supplement changes gives you useful data. PeriPlan lets you log symptoms consistently so you can see whether things are shifting.
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