How hormones, vitamins, thyroid function, and metabolic markers directly influence anxiety, mood swings, and depression — and why a blood test should be the first step before medication.
Anxiety, mood swings, and low mood can be driven by biomarkers that standard GP testing misses — including low progesterone, elevated cortisol, suboptimal Free T3, deficient vitamin D, low magnesium, borderline B12 and folate, and insulin resistance. A comprehensive blood test checking all of these can identify whether a hormonal, nutritional, or metabolic cause is contributing to your mental health symptoms before medication is considered. TrueVitals tests every one of these in the Ultimate panel — 110 biomarkers with a 60-page personalised report for £349.
Mental health conditions are primarily treated with medication in the UK. Antidepressants are the third most prescribed drug class in the country. Yet in the vast majority of cases, no blood test is performed before prescribing. The assumption is that anxiety and depression are psychological conditions requiring psychological or pharmaceutical treatment. While this is true in many cases, a significant proportion of people experiencing mood symptoms have identifiable biochemical contributors that could be addressed through nutritional or hormonal intervention — if anyone thought to test for them.
Progesterone — the calming hormone nobody checks:
Progesterone activates GABA receptors in the brain, producing a calming, anxiolytic effect. Low progesterone causes anxiety, irritability, insomnia, and mood swings — particularly in the second half of the menstrual cycle (luteal phase). Women who experience premenstrual anxiety, rage, or emotional instability often have low progesterone relative to oestradiol. This is testable, identifiable, and addressable — but GPs almost never check progesterone outside of fertility investigations. One of our customers had a progesterone of 1.8 nmol/L in her luteal phase, when it should be 5-25+. This single finding explained her mood swings entirely.
Cortisol — the anxiety accelerator:
Elevated cortisol creates a state of physiological hypervigilance — racing thoughts, difficulty relaxing, physical tension, and a sense of dread that has no obvious cause. Many people diagnosed with generalised anxiety disorder have chronically elevated cortisol from work stress, poor sleep, caffeine overconsumption, or overtraining. Addressing the cortisol driver can reduce anxiety symptoms without medication.
Free T3 — the metabolic mood link:
Low Free T3 does not just cause fatigue. It slows neurotransmitter production and turnover, contributing to low mood, apathy, poor motivation, and emotional flatness. The pattern of normal TSH with low Free T3 is common in stressed, under-eating individuals and is invisible to standard thyroid testing. Many people prescribed antidepressants for low mood actually have a thyroid conversion issue that would respond to nutritional intervention.
Vitamin D — the mood regulator:
Vitamin D receptors are abundant in brain regions involved in mood regulation. Deficiency is consistently associated with increased risk of depression and anxiety in clinical studies. At 38 nmol/L you are deficient. Supplementing to optimal levels (75-150 nmol/L) has been shown to improve mood symptoms in deficient individuals, sometimes significantly.
Magnesium — the anti-anxiety mineral:
Magnesium is a cofactor for over 300 enzymatic reactions including neurotransmitter synthesis and GABA receptor function. Borderline magnesium (just inside the reference range but well below optimal) is extremely common in active, stressed individuals and contributes to anxiety, muscle tension, poor sleep, and headaches. Serum magnesium of 0.72 mmol/L is technically normal but functionally inadequate for someone under physiological stress.
B12 and folate — the methylation connection:
Both vitamins are essential for methylation, the biochemical pathway that produces serotonin, dopamine, and norepinephrine. Suboptimal B12 or folate impairs neurotransmitter production and can cause low mood, irritability, and cognitive symptoms. MTHFR gene variants, which affect folate metabolism, are present in approximately 40% of the population and can be partially compensated for with methylfolate supplementation.
Insulin resistance — the mood swing generator:
Blood sugar instability caused by insulin resistance produces mood swings, irritability, anxiety between meals, and emotional reactivity that resolves temporarily after eating. This pattern is often misidentified as an anxiety disorder when it is actually a metabolic problem. Fasting insulin and HOMA-IR identify it. Dietary modification resolves it.
Iron deficiency — the overlooked contributor:
Iron is essential for dopamine synthesis. Low ferritin is associated with increased anxiety and restless legs syndrome. Depleted iron stores impair the brain's ability to produce the neurotransmitter most associated with motivation, pleasure, and calm focus.
The case for testing before medicating:
If low progesterone, elevated cortisol, suboptimal Free T3, deficient vitamin D, borderline magnesium, and low folate are collectively contributing to someone's anxiety and low mood, an antidepressant addresses none of these root causes. It may mask the symptoms while the underlying biochemical drivers persist. A comprehensive blood test identifies which — if any — of these factors are present, allowing targeted intervention before or alongside medication.
TrueVitals' 60-page personalised report does not diagnose mental health conditions. It identifies biochemical factors that may be contributing to your symptoms and provides specific, actionable recommendations for addressing them. This is information your GP does not have and cannot provide without comprehensive testing.