Pregnenolone Blood Test: Normal Ranges, Causes & What Your Results Mean

What Is Pregnenolone?

Pregnenolone is a steroid hormone often referred to as the "mother of all hormones" because it serves as the master precursor from which virtually all other steroid hormones are synthesised. It is the first step in the steroidogenesis pathway - the biochemical cascade that produces cortisol, DHEA, progesterone, testosterone, oestrogen, and aldosterone.

Pregnenolone is synthesised primarily in the adrenal glands, but it is also produced in the gonads (ovaries and testes), brain, liver, and skin. The conversion of cholesterol to pregnenolone is catalysed by the enzyme cytochrome P450 side-chain cleavage (CYP11A1) and represents the rate-limiting step in steroid hormone production. This reaction occurs within the mitochondria and is stimulated by adrenocorticotrophic hormone (ACTH) in the adrenal glands and by luteinising hormone (LH) in the gonads.

Beyond its role as a precursor, pregnenolone has direct biological activity, particularly in the brain. It functions as a neurosteroid - a steroid that modulates neurotransmitter receptors directly. Pregnenolone and its sulphated form (pregnenolone sulphate) interact with GABA-A receptors, NMDA receptors, and sigma-1 receptors, influencing memory formation, mood regulation, neural protection, and cognitive function. Research suggests that pregnenolone may have neuroprotective, anti-inflammatory, and mood-enhancing properties independent of its downstream hormones.

Pregnenolone levels naturally decline with age. By the time adults reach their 70s, pregnenolone levels may be 60% lower than they were in their 30s. This decline parallels the age-related reduction in other steroid hormones and has generated interest in pregnenolone as a potential marker of hormonal ageing and adrenal reserve.

Why Is Pregnenolone Tested?

Pregnenolone testing is used in specific clinical scenarios, predominantly related to adrenal function and steroidogenesis disorders:

• Congenital adrenal hyperplasia (CAH) diagnosis: Certain forms of CAH, particularly 3-beta-hydroxysteroid dehydrogenase (3β-HSD) deficiency, cause elevated pregnenolone because the enzyme needed to convert it to downstream hormones is deficient or absent.
• Adrenal insufficiency assessment: In primary adrenal insufficiency (Addison's disease), the entire steroidogenesis pathway is compromised. Pregnenolone may be low alongside cortisol and other adrenal hormones.
• Hormonal imbalance investigation: When patients present with symptoms suggesting widespread hormonal deficiency, fatigue, low mood, poor memory, reduced libido, and standard hormone tests are inconclusive, pregnenolone can provide insight into the upstream capacity of steroidogenesis.
• Functional medicine and longevity assessment: Pregnenolone is measured as part of comprehensive hormonal panels to assess adrenal reserve, hormonal ageing, and overall neuroendocrine function. While not part of routine NHS testing, it is increasingly requested in private health screening.
• Monitoring supplementation: Some patients take pregnenolone supplements (available over the counter in the US, though not routinely recommended in UK clinical practice). Blood levels may be monitored to assess dosing.
• Cognitive decline investigation: Reduced pregnenolone levels have been observed in patients with Alzheimer's disease and other neurodegenerative conditions, though the clinical significance of this finding is still being investigated.
• Chronic fatigue and stress syndromes: In the context of chronic stress, the "pregnenolone steal" hypothesis suggests that the body preferentially converts pregnenolone toward cortisol production at the expense of sex hormones (DHEA, testosterone, oestrogen). While this concept is debated in academic medicine, it informs some functional medicine approaches.

Normal Ranges

Pregnenolone is measured in nanomoles per litre (nmol/L) or nanograms per decilitre (ng/dL). Reference ranges vary between laboratories and are influenced by age, sex, and the time of day (pregnenolone follows a mild diurnal rhythm, tending to be higher in the morning). The following are typical adult reference ranges:

Category	Normal Range (nmol/L)	Normal Range (ng/dL)	Notes
Adult men	1.0–10.6 nmol/L	33–350 ng/dL	Wide physiological range
Adult women (follicular phase)	0.6–8.8 nmol/L	20–290 ng/dL	Varies with menstrual cycle
Adult women (luteal phase)	1.2–12.1 nmol/L	40–400 ng/dL	Higher due to corpus luteum activity
Postmenopausal women	0.5–5.5 nmol/L	17–180 ng/dL	Declines with reduced gonadal function
Older adults (over 70)	0.3–4.5 nmol/L	10–150 ng/dL	Age-related decline in steroidogenesis

Due to the wide reference ranges and the influence of multiple physiological variables, a single pregnenolone measurement must be interpreted in conjunction with other hormones (cortisol, DHEA-S, testosterone, oestradiol, progesterone) and clinical symptoms. Trends over time are often more informative than a single reading.

What Do High Pregnenolone Levels Mean?

Elevated pregnenolone can indicate a block in downstream steroid hormone production or increased upstream stimulation:

• Congenital adrenal hyperplasia (3β-HSD deficiency): This rare enzyme deficiency prevents pregnenolone from being converted to progesterone and further downstream hormones. Pregnenolone and its metabolites accumulate. Affected individuals may present with salt-wasting crises in infancy, ambiguous genitalia, or, in milder late-onset forms, premature adrenarche, acne, and menstrual irregularity.
• Pregnenolone supplementation: Exogenous pregnenolone intake will elevate blood levels. In the US, pregnenolone is available as an over-the-counter supplement and may be taken without medical supervision.
• ACTH-producing tumours: Ectopic ACTH production (e.g., from small-cell lung carcinoma) or pituitary Cushing's disease drives excessive adrenal steroidogenesis, potentially elevating pregnenolone alongside cortisol.
• Ovarian or adrenal tumours: Rarely, steroid-producing tumours can elevate pregnenolone as part of broader hormonal excess.
• Stress response: Acute physiological or psychological stress stimulates the HPA axis, increasing ACTH and driving pregnenolone production. This is usually a transient, adaptive response.
• Pregnancy: Pregnenolone levels rise significantly during pregnancy due to placental and adrenal steroid production.

What Do Low Pregnenolone Levels Mean?

Low pregnenolone levels suggest reduced capacity for steroid hormone production, with various potential causes:

• Age-related decline: The most common cause. Pregnenolone production naturally decreases with age, mirroring the decline in DHEA and other adrenal hormones. This is a normal part of ageing but may contribute to symptoms such as fatigue, reduced cognitive sharpness, and mood changes.
• Adrenal insufficiency: Primary adrenal failure (Addison's disease) reduces production of all adrenal steroids, including pregnenolone. Secondary adrenal insufficiency (pituitary ACTH deficiency) has a similar downstream effect.
• Chronic stress and HPA axis dysregulation: Prolonged stress may eventually deplete adrenal reserve and reduce pregnenolone output. This is sometimes described in functional medicine as "adrenal fatigue," though this term is not recognised in mainstream endocrinology.
• Cholesterol deficiency: Since pregnenolone is synthesised from cholesterol, extremely low cholesterol levels (whether from severe malnutrition, aggressive statin therapy, or genetic conditions such as Smith-Lemli-Opitz syndrome) could theoretically limit pregnenolone production. In practice, this is rarely clinically significant at typical statin doses.
• Hypothyroidism: Thyroid hormones support adrenal steroidogenesis. Severe hypothyroidism may reduce pregnenolone production.
• Chronic illness: Prolonged systemic illness, including autoimmune diseases and chronic infections, can suppress the neuroendocrine axis and reduce steroid hormone production.
• Mitochondrial dysfunction: Since the conversion of cholesterol to pregnenolone occurs within mitochondria, conditions that impair mitochondrial function may theoretically reduce pregnenolone synthesis.
• Medications: Ketoconazole (an antifungal that inhibits steroidogenic enzymes), some opioids, and prolonged high-dose corticosteroid use (which suppresses ACTH) can lower pregnenolone.

How to Improve Your Pregnenolone Levels

Supporting Natural Production

• Ensure adequate cholesterol intake: Pregnenolone is synthesised from cholesterol. Extremely restrictive low-fat diets may theoretically limit substrate availability. Include healthy fat sources such as eggs, oily fish, avocados, nuts, and olive oil.
• Prioritise sleep: Steroid hormone production follows a circadian rhythm, with peak synthesis occurring during sleep. Aim for 7–9 hours of quality sleep per night. Poor sleep directly impairs HPA axis function and hormone production.
• Manage stress: Chronic stress can deplete adrenal hormone reserves over time. Effective stress management - through regular exercise, mindfulness, meditation, adequate rest, and social connection - supports HPA axis health.
• Regular exercise: Moderate-intensity exercise (150 minutes per week minimum) supports healthy hormonal function. Avoid overtraining, which can suppress the HPA axis.
• Optimise vitamin and mineral status: Several micronutrients are cofactors in steroidogenesis. Vitamin C (adrenal glands contain the highest concentration of vitamin C in the body), B vitamins (particularly B5/pantothenic acid and B6), magnesium, and zinc all support adrenal hormone production.
• Maintain healthy thyroid function: Thyroid hormones support adrenal steroidogenesis. If you have hypothyroidism, ensure adequate treatment with levothyroxine.

Supplementation

• Pregnenolone supplements: Available in some countries (primarily the US) as an over-the-counter supplement, typically in doses of 5–50 mg daily. In the UK, pregnenolone is not widely available as a supplement and is not routinely recommended by NHS guidelines. If considering supplementation, consult a qualified healthcare professional, as exogenous pregnenolone can affect the balance of downstream hormones.
• DHEA: As a downstream metabolite of pregnenolone, DHEA supplementation is sometimes used in adrenal insufficiency under medical supervision. It does not directly raise pregnenolone but may address some of the same symptoms.

Medical Management

• Treat adrenal insufficiency: If low pregnenolone is part of broader adrenal failure, hydrocortisone and fludrocortisone replacement (for Addison's disease) or DHEA supplementation may be indicated under specialist supervision.
• Investigate and treat underlying causes: Thyroid disorders, chronic infections, autoimmune conditions, and medication effects should be identified and managed.

When Should You Get Tested?

Consider a pregnenolone blood test if:

• You experience persistent fatigue, brain fog, poor memory, or reduced cognitive function that is not explained by other conditions.
• You have low libido, mood changes, or depression and standard hormone tests (cortisol, testosterone, oestradiol) are inconclusive.
• You have been diagnosed with or are being investigated for congenital adrenal hyperplasia.
• You have adrenal insufficiency and want a complete assessment of steroidogenesis.
• You want a thorough hormonal profile as part of longevity or anti-ageing assessment.
• You are taking pregnenolone or DHEA supplements and need monitoring.
• You have chronic stress symptoms and want to assess your adrenal hormonal reserve.
• You are in your 50s or older and want to understand age-related hormonal changes.

For the most accurate results, the blood sample should be drawn in the morning (between 8am and 10am) when steroid hormone levels are at their peak. Inform your clinician about any medications or supplements you are taking, as these can affect results.

Which Lola Health Tests Include Pregnenolone?

Pregnenolone is an advanced hormonal biomarker that provides insight into your body's capacity for steroid hormone production. Lola Health includes pregnenolone in our full testing panels:

• Peak Insights - our most detailed health screen, including pregnenolone alongside cortisol, DHEA-S, testosterone, oestradiol, and a full panel of hormonal, metabolic, and cardiovascular biomarkers.
• Hormone 7 - a focused hormonal panel covering key reproductive and adrenal hormones for a detailed picture of hormonal balance.
• Vital Check — a broad wellness screen covering hormonal, metabolic, and cardiovascular health markers.
• Core Health — an essential health check providing fundamental hormonal and metabolic insights.

All Lola Health tests use venous blood draws for clinical-grade accuracy. Your results are reviewed by qualified healthcare professionals who provide personalised recommendations based on your complete hormonal profile.