What is progesterone and what does it do?

6 min
Updated Dec 8th, 2023

Whether you’re trying to conceive, you want to in the future, or you’ve been struggling to conceive, it helps to know as much as possible about the science behind it all so that you can give yourself the best chance. Progesterone is a hormone that you want around! Let’s run through why.

Progesterone plays a significant part in female infertility treatment because it supports implantation and pregnancy. In fact, you may struggle to get pregnant or stay pregnant if you don’t have enough progesterone. Your progesterone levels should go up after one of your ovaries releases an egg. The progesterone then assists the uterus in becoming receptive so that the fertilised egg can implant successfully. Without enough progesterone, the egg won’t be able to implant.

What is progesterone?

There’s a rather intricate hormone network within your body that affects your fertility. Progesterone is one of these hormones and it’s released by the corpus luteum, which is formed from the empty follicle in the ovary. Because of this, it’s often known as the ‘pregnancy hormone’. Progesterone supports the early stages of your pregnancy and the change (reduction)in progesterone levels is what starts menstruation.

What is the main function of progesterone?

The main function of progesterone is to ready the endometrium (lining of your uterus) for a fertilised egg to successfully implant and develop. If pregnancy doesn’t happen, progesterone levels drop the endometrium sheds, known as a ‘period’. And if conception successfully takes place, the progesterone will continue to increase and support the pregnancy.

Progesterone and menstruation

Your ovary releases an egg (ovulation) from a sac called a follicle around the middle of your menstrual cycle. The empty follicle forms a body called the corpus luteum, which supports the beginning of your pregnancy if conception happens during that cycle. Progesterone production starts when the corpus luteum forms from the empty egg follicle. Progesterone then gets to work creating the ideal, cosy conditions for a fertilised egg to implant, with improved blood supply to the thickened lining.

If the egg isn’t fertilised, then the progesterone levels go down as the corpus luteum shrivels up and your period starts.

Progesterone and pregnancy

If the egg is fertilised by the sperm, then the progesterone continues to increase and the corpus luteum doesn’t break down. Progesterone is crucial during pregnancy as it ensures that your uterine lining has become receptive. The lining will support the fertilised egg as it develops into an embryo and then a foetus. This progesterone-induced lining has plenty of blood vessels. These blood vessels provide nutrients for the embryo. The progesterone production is eventually taken over by the placenta. 

As your pregnancy progresses, your progesterone levels will increase and reach the highest level during the third trimester. The high progesterone levels will stop your body from having a period and it’ll also prevent uterine contractions (for preterm labour). Lower levels of progesterone may make it more difficult for you to conceive and you will be at a higher risk of miscarriage.  And as progesterone is such a super-hormone it’ll also help your body to prepare for breastfeeding. 

Before ovulation stops with menopause, your progesterone levels will have been decreasing in the years leading up to this.

How does your body produce progesterone?

Your body produces progesterone via that temporary body we mentioned earlier — the corpus luteum. The corpus luteum is generated after you ovulate (release an egg from your ovary) from the empty follicle. This gland will also serve to maintain progesterone levels throughout your pregnancy. Progesterone is also made by your placenta and your adrenal glands.

What is considered a normal level of progesterone?

It’s normal for the levels of progesterone to go up and down throughout your menstrual cycle. Progesterone levels will go up after ovulation and need to be high enough to cause important changes in your uterine lining for successful implantation. The progesterone levels will keep on going up if you’re pregnant. 

If you want to know if your progesterone levels are where they should be, talk to your doctor. Symptoms of low progesterone include irregular menstrual periods, headaches, weight gain, hot flushes, miscarriage, spotting during pregnancy or infertility and difficulty conceiving.

Low progesterone can be a result of things like stress or obesity which can be treated by making lifestyle changes. But low progesterone can also be a result of polycystic ovarian syndrome (PCOS) due to insulin resistance, often treated with metformin. Unfortunately, metformin doesn’t normalise insulin resistance in PCOS and can have some unmanageable side effects. Inofolic Alpha is a natural way to reduce insulin resistance and manage PCOS symptoms, without side effects.

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When should you take progesterone?

Your doctor may prescribe you with progesterone supplement if you:

  • Need to prevent pregnancy (the traditional progestogen-only pill (POP) or the desogestrel progestogen-only pill can stop ovulation).
  • Have perimenopause symptoms (perimenopause means ‘around menopause’ and marks the transition to menopause which can start ten years before menopause starts).

Can progesterone levels be naturally increased with certain foods?

Food doesn’t contain progesterone. However, eating nutrient-rich foods full of vitamins and including food compounds may help to maintain healthy progesterone levels, but research so far is very limited. It’s always beneficial for the good of your health to eat a balanced diet though!

Vitamins that are thought to help include:

  • Vitamin C — found in citrus fruits and cruciferous veggies (broccoli, cabbage, cauliflower).
  • Zinc — found in shellfish, eggs, chickpeas and cashews.
  • Magnesium — found in beans, nuts, seeds and green vegetables.
  • Vitamin B — found in spinach, walnuts and carrots.

We hope that’s given you a general overview of this helpful hormone. It’s useful to get acquainted with progesterone as it plays an important role in your menstrual cycle and pregnancy. By ensuring that your progesterone levels are as they should be, you can prevent some debilitating symptoms, some of which you might not have realised are down to low levels of progesterone! 


K J Meenakumari 1, S Agarwal, A Krishna, L K Pandey. Effects of metformin treatment on luteal phase progesterone concentration in polycystic ovary syndrome. The Brazilian Journal of Medical and Biological Research 2004 Nov;37(11):1637-44.

Stefania Greco, et al. Phytoprogestins: Unexplored Food Compounds with Potential Preventive and Therapeutic Effects in Female Diseases. Nutrients. 2021 Dec; 13(12): 4326.

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