Hormone Health Hub: Expert Insights on Testing, Balance & Better Living — vitamin D and serotonin

Did you know that low vitamin D could be disrupting your sleep? Research shows that vitamin D plays a key role in serotonin and melatonin production — the hormones that regulate your sleep-wake cycle. Dr. Kate Placzek explores the science behind the vitamin D–sleep connection, what else low vitamin D affects, and how to find out if deficiency is at the root of your sleep problems.

Had your vitamin D tested and left confused by the result? You are not alone. Different agencies have different opinions on what counts as deficient, sufficient or optimal — and the gap between “normal” and “optimal” matters more than most people realise. Dr. Jillian Harrington breaks down the reference ranges, explains what your result actually means, and outlines how to work towards the level that is right for your health.

As the days shorten and sunlight fades, four key hormonal systems come under pressure: vitamin D, serotonin, cortisol and melatonin. For those susceptible to Seasonal Affective Disorder (SAD), the disruption of these interconnected rhythms can trigger depression, fatigue, poor sleep and low mood. This article explains the science behind the SAD hormone pattern — and what you can do to support your body through the darker months.