Vitamin D Deficiency in Women: The Symptoms Nobody Connects
Over 40% of adults are vitamin D deficient — and women are disproportionately affected. Here's what low vitamin D actually feels like, and how to fix it.
Vitamin D is technically not a vitamin — it's a hormone precursor. Every cell in your body has vitamin D receptors, and it influences gene expression, immune function, mood regulation, calcium metabolism, and hormone production. When it's low, the effects are widespread and often misattributed to other causes.
Over 40% of adults in the United States are vitamin D deficient, and the numbers are higher for women, people with darker skin tones, those who live in northern latitudes, and anyone who spends most of their time indoors. The standard reference range for "normal" vitamin D (above 20 ng/mL) is widely considered inadequate by functional medicine practitioners — optimal levels for health are generally considered to be between 50-80 ng/mL.
The symptoms most women don't connect to vitamin D:
Persistent fatigue and low energy, bone and muscle aches, frequent illness or slow recovery from infections, low mood and seasonal depression, hair loss, poor sleep quality, and brain fog. Many women with these symptoms are tested for thyroid issues, anaemia, and depression — but vitamin D is rarely the first thing checked.
Vitamin D and hormones:
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Vitamin D directly supports progesterone production and helps regulate the immune system's role in reproductive health. Low vitamin D is associated with higher rates of PCOS, endometriosis, fibroids, and fertility challenges. It also plays a role in insulin sensitivity — deficiency is linked to higher rates of insulin resistance and type 2 diabetes.
How to optimise your levels:
Sun exposure remains the most effective way to raise vitamin D — 15-30 minutes of midday sun on arms and legs (without sunscreen) several times per week is sufficient for most people in sunny climates. For supplementation, vitamin D3 (cholecalciferol) is the preferred form. Critically, vitamin D should be taken with vitamin K2 (specifically MK-7 form) — D3 increases calcium absorption, and K2 directs that calcium to your bones rather than your arteries.
Aim to get your 25-OH vitamin D level tested before supplementing, and retest after 3 months to confirm your dose is adequate. Most adults need 2,000-5,000 IU daily to maintain optimal levels.
This post contains affiliate links. I only recommend products I personally use and trust. Always consult your healthcare provider before starting any new supplement.
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