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

What Is Progesterone?

Progesterone is a steroid hormone primarily produced by the corpus luteum in the ovary following ovulation. During pregnancy, the placenta becomes the major source from about 10 weeks gestation. In men, smaller amounts are produced by the adrenal glands and testes as a precursor to other steroid hormones.

Progesterone's primary role is to prepare the uterine lining (endometrium) for implantation of a fertilised egg and to maintain early pregnancy. It also has calming effects on the central nervous system, supports bone density, and modulates immune function. Progesterone and oestrogen work in balance throughout the menstrual cycle - disruption of this balance underlies many gynaecological symptoms.

Why Is Progesterone Tested?

• Confirming ovulation - a mid-luteal phase progesterone above 30 nmol/L confirms ovulation occurred
• Fertility investigation - inadequate progesterone (luteal phase defect) can impair implantation
• Early pregnancy monitoring - low progesterone in early pregnancy may indicate ectopic pregnancy or miscarriage risk
• Menstrual irregularities - investigating causes of irregular, heavy, or absent periods
• Hormone replacement therapy - monitoring progesterone levels during HRT

Normal Ranges

Timing is critical: for ovulation confirmation, blood should be taken 7 days before the expected period (day 21 of a 28-day cycle, day 28 of a 35-day cycle).

What Do High Progesterone Levels Mean?

• Pregnancy - the most common cause of significantly elevated progesterone
• Ovulation - normal mid-luteal rise confirms ovulation
• Ovarian cysts - corpus luteum cysts can produce excess progesterone
• Congenital adrenal hyperplasia - 21-hydroxylase deficiency causes progesterone accumulation
• Progesterone supplementation, IVF protocols and HRT raise levels
• Adrenal tumours, rare progesterone-secreting tumours

What Do Low Progesterone Levels Mean?

• Anovulation - the most common cause; no corpus luteum means no progesterone surge
• Luteal phase defect - short or inadequate luteal phase with insufficient progesterone for implantation
• Threatened miscarriage - declining progesterone in early pregnancy is concerning
• Ectopic pregnancy - progesterone levels are often lower than in viable intrauterine pregnancy
• PCOS - chronic anovulation means persistently low progesterone
• Hypothalamic amenorrhoea - stress, low body weight, or excessive exercise suppress ovulation
• Perimenopause - irregular ovulation leads to erratic progesterone levels

How to Support Healthy Progesterone Levels

• Support ovulation - regular ovulation is the primary driver of progesterone; address underlying causes of anovulation
• Maintain healthy body weight - both underweight and overweight disrupt ovulation
• Manage stress - cortisol competes with progesterone for receptor binding and high stress suppresses ovulation
• Adequate vitamin B6 - B6 supports corpus luteum function; found in poultry, fish, potatoes, and chickpeas
• Zinc and magnesium — both minerals support healthy hormone production
• Discuss progesterone support — if levels are low and you are trying to conceive, your doctor may prescribe progesterone pessaries or capsules

When Should You Get Tested?

• You are trying to conceive and want to confirm ovulation
• You have irregular, heavy, or absent periods
• You are in early pregnancy and your GP wants to check viability
• You are experiencing perimenopausal symptoms
• As part of a comprehensive fertility or hormone panel

Which Lola Health Tests Include Progesterone?

Progesterone is included in our Hormone 7 panel. Available as an add-on with any Lola Health blood test. Test on day 21 of your cycle (or 7 days before expected period) for ovulation confirmation.