Does a short luteal phase always mean low progesterone?

Written by: Dr. Amy Beckley, PhD, Founder and Inventor of the Proov test the first and only FDA-cleared test to confirm successful ovulation at home.

Written on: 12/13/21

Does a short luteal phase always mean low progesterone

Keep reading to learn more about short luteal phase and low progesterone.

If there’s one thing that’s true about the fertility world, it’s that there are a lot of new terms to learn. If you’re familiar with Proov already, you may have heard us throw around terms like, “short luteal phase,” “low progesterone,” or “luteal phase defect.”

While all these terms are related, they don’t exactly mean the same thing. Keep reading to learn more about short luteal phase and low progesterone.

What is a short luteal phase and what causes it?

The luteal phase is the second half of your cycle, lasting from ovulation to the first day of your next period. It is a critical time during your cycle, especially if you are trying to conceive.

After ovulation, the empty follicle forms something called the corpus luteum, which starts producing the hormone, progesterone. Progesterone’s job is to prepare the uterine lining for implantation and pregnancy by making it “sticky” enough so that a newly fertilized egg can attach itself comfortably.

The “implantation window” — the time when progesterone levels should be elevated so that the uterine lining is prepared to receive the embryo — typically lasts about 4 days. Implantation most commonly occurs between days 7 and 10 past peak fertility (i.e. a positive ovulation test).

Ideally, your luteal phase should last at least 11 days after ovulation, to allow the embryo enough time to implant. Any luteal phase that lasts less than 11 days is considered a “short luteal phase.”

Typically, low progesterone levels cause a short luteal phase. Sustained progesterone production is what keeps the luteal phase long.

When progesterone levels aren’t high enough or drop too soon, the uterine lining is no longer receptive to an embryo and this tells your body that implantation and pregnancy didn’t occur. So, your uterine lining starts shedding and your period begins.

Since the implantation window lasts until day 10 after peak fertility, a luteal phase shorter than that length can make it more difficult — although not impossible — to get pregnant.

What is low progesterone and what causes it?

As we mentioned, progesterone is the dominant hormone during the second half of your cycle. It needs to remain elevated through the entire implantation window to allow for an optimal luteal phase length and the best possible chance at implantation and pregnancy.

The corpus luteum produces progesterone during the luteal phase. Sometimes the corpus luteum does not produce enough progesterone which, as we saw, may cause the uterus to start shedding its lining during the implantation window.

Low progesterone levels during the luteal phase can cause short luteal phase, incomplete implantation, early miscarriage, or infertility.

Low progesterone has many various causes and, sometimes, it can be difficult to pinpoint the exact culprit. That said, certain disorders have been connected to low progesterone and may put you at a higher risk for luteal phase deficiency:

  • Endometriosis
  • PCOS
  • Thyroid imbalances, such as hypothyroidism
  • Abnormally low or high body weight
  • Increased cortisol production (due to stress)

If you are concerned about any of the aforementioned issues, we recommend consulting your doctor.

Does a short luteal phase always mean low progesterone

Low progesterone has many various causes and, sometimes, it can be difficult to pinpoint the exact culprit.

Does a short luteal phase always mean low progesterone?

If your period comes less than 11 days after your first positive ovulation test (i.e. peak fertility), this could be a sign of a short luteal phase. While short luteal phases typically indicate insufficient progesterone production, you’d still need a progesterone blood test, PdG urine test, or endometrial biopsy to confirm.

According to the American Society of Reproductive Medicine, a short luteal phase may have three potential causes, all of which revolve around progesterone.

  • Low duration progesterone: When progesterone levels are good, but not for long enough. When they drop too soon, the period comes too early.
  • Low progesterone levels: Although progesterone levels may not suddenly drop sooner than expected, they are not high enough to sustain a healthy luteal phase.
  • Endometrial progesterone resistance: This involves an impaired response from the uterine lining to the secretion of progesterone during the luteal phase. This means that the uterus doesn’t become receptive, even with progesterone present. It’s common in those with endometriosis.

While a short luteal phase usually means low progesterone too, it’s important to note that low progesterone does not always manifest itself in a short luteal phase. If you have a healthy luteal phase length, but are still having trouble conceiving, you may want to get your levels checked — especially since the fix for low progesterone is often so simple!

How can I tell if I have a luteal phase defect or low progesterone?

The most obvious sign of luteal phase defect or low progesterone is a luteal phase that lasts less than 11 days. Your period may start suddenly or you may experience spotting (sometimes brown) for several days before the true start of your next period.

Another sign of low progesterone may be the inability to get pregnant, especially if you’re timing intercourse around your fertile window and have already confirmed your partner has healthy sperm.

The most devastating and traumatic sign of low progesterone may be recurrent early miscarriages. Studies show up to 75% of early miscarriages are caused by failed implantation.

But we believe you shouldn’t have to experience any difficulty conceive or early miscarriages to know where your progesterone levels stand. That’s why we always recommend testing levels sooner rather than later, to prevent any necessary heartbreak or struggle.

While progesterone can be tested in blood, PdG (progesterone marker) testing in urine is non-invasive and allows for testing levels over time. Studies show PdG levels in first morning urine correlate to an average of all progesterone levels from the previous day.

Proov Confirm PdG tests are the first and only FDA cleared tests to confirm ovulation quality at home. High quality ovulation refers to an ovulatory event in which an egg is released and PdG levels remain elevated for long enough during the implantation window to allow for the best possible chance at pregnancy.

Does a short luteal phase always mean low progesterone

Proov Confirm PdG tests are the first and only FDA cleared tests to confirm ovulation quality at home.

The patented Proov PdG testing protocol recommends testing levels on days 7-10 past peak fertility — the implantation window — to confirm ovulation quality.  Studies show elevated PdG levels during the luteal phase correlate to a 92% chance at successful pregnancy.

If your Ovulation Score is between 60 and 80, this could be a sign that even though you are ovulating and can absolutely conceive, your PdG levels might need a little extra support to give you the best possible chance at pregnancy. Luckily, there are plenty of ways to give your levels a little extra boost!

The luteal phase is a critical part of your cycle, especially when trying to conceive! Understanding the ideal luteal phase length and how progesterone comes into play can help you reach your fertility goals faster. 

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“Hormone balance plays a huge role in fertility, and understanding what’s going on with your hormones doesn’t have to be such a mystery.

It’s actually way easier than most people realize.” 

— Amy Beckley, Proov Founder