LH - Ovulationtests: What they really tell you and the risks they pose

You can know when you’re ovulating in an instant. At least that's what the ovulation test kit ads tell you. Simply hold the test strip in your urine, see whether the test is negative or positive - and then use condoms (if you want contraception) or have sex (if you want children).

The conceptof ovulation testing this way is simple and straightforward: you measure how much of the luteinizing hormone (LH) is present in your urine. LH is one of the hormones that control your cycle. It triggers your ovulation, and is important for the formation of the corpus luteum, which in turn produces the hormone progesterone.

However, the LH level varies not only within the cycle, but also from woman to woman - and sometimes the same woman during her fertile years across different cycles. This is shown by the following statistics

  • In the first phase of the cycle, the LH normal value of a healthy girl or a healthy younger woman is 1.9 to 12.5 international units per liter (IU/l for short).
  • Just before ovulation, at the so-called LH peak, the concentration is 8.7 to 76.3 U/l.
  • Afterwards, the concentration drops sharply and is 0.5 to 16.9 U/l in the 2nd half of the cycle1.

However, for women who have to take medication, who have used hormonal contraception recently, who are underweight  or are already in menopause, the situation can be quite different. They can read little or nothing from LH tests. But more on that later.

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What your LH value wants to tell you

Let's assume that everything is fine with you. You haven't taken any hormonal contraceptives or medications in the last few months, you feel completely fit, and you want to determine your most fertile days. So you order LH tests, which are available on the Internet for as little as 20 cents each.

The phase for LH testing begins two weeks plus three or four days before the start of your expected period. The rule of thumb is therefore: your cycle length minus 14 days minus a few days lead time. At 28 days, it would then make sense to start testing around the 9th day of your cycle, and at 36 days, around the 18th day of your cycle2. And from now on you test daily at the same time until your LH peak is indicated, the test is positive and ovulation follows.

If everything works out, your LH test will reliably show you the highest LH level, the LH peak. It takes 24 to 36 hours from this point to ovulation3. If you are planning to have a baby, you should therefore have sex without protection as soon as possible, because your egg can be fertilized for a maximum of one day. If you definitely don't want a baby (yet), please don't feel safe afterwards. The accuracy of LH tests is limited.

Problem 1: Women are not all the same

Many girls and women, unfortunately, do not have the "normal" levels of LH. Women with polycystic ovary syndrome and women going through menopause live with permanently elevated LH levels. Permanently low levels occur, for example, if you are underweight, taking hormonal contraceptives or have a malfunction of the pituitary gland1,4,5. Other hormonal medications, antibiotics, psychotropic drugs and many underlying diseases can also affect the levels. If you keep getting positive test results, you should see your gynecologist to find out what is causing them. The same applies if your tests remain negative for a long time.

Problem 2: Not all LH tests are the same.

Not every test responds equally reliably to hormonal fluctuations in every woman and every lifestyle. The higher the IU/l value printed on the package, the later the LH test will show a peak - so the less sensitive the test. Particularly sensitive LH tests react as early as 10 or 20 IU/l. However, this is only meaningful if your value is permanently below this at the beginning and end of the cycle. Therefore, at the beginning of your measurements with LH tests, it is also useful to first determine what your personal pattern is and when your peak normally appears. If you have too many negative or positive results, you should compare tests with different sensitivities and, if necessary, go to your doctor for a check-up.

Problem 3: Which urine only do I take?

The third challenge is directly related to the second: Many women take morning urine for the test because, after all, it is what we are advised for  pregnancy testing. But with the highly concentrated urine, the chance of a false positive test result increases3.

Also an issue: Drink a lot directly before testing. This may dilute the urine so much that no positive test result is shown despite ovulation. Experts recommend not drinking for at least four hours before the LH test3.

Problem 4: Fluctuations during the course of the day

The output of LH does not happen evenly, but in spurts throughout the day. Thus, women may test both positive and negative on the same day. For this reason, it is recommended to decide on a time of day and to always measure the LH level at this time with the individually most suitable test (see problem 2) in order to recognize the personal pattern4.

Problem 5: Definitely no contraceptive!

Some women who do not want to have children think that once they have determined their personal LH peak, any other contraception can be omitted one day after ovulation. But as problems 1 to 4 already show, the test result can quickly be off the mark. Forget a test here, an approaching infection there, an incipient hormone disorder there - and a value is false positive or negative and a woman is unintentionally pregnant. From the onset of menopause (perimenopause), LH tests permanently lose their significance. However, ovulation and pregnancies are still possible.

Also remember: Before ovulation, LH tests definitely do not show all fertile days. This is because sperm can wait up to five days in the female body for the egg.

Problem 6: Unreliable pillar of fertility planning.

Yes, the LH test can be a part of  family planning. But if you really want to know your body better, other methods are more promising. Taking your basal body temperature every morning and recording the curve is one way. Cycle trackers, such as Daysy, make it more convenient and accurate, and you benefit from the experience of millions of cycles. In addition, you can also monitor your cervical mucus every morning and see the pattern behind it4. You are also free to combine different methods - which can include LH testing.

Daysy - Your personal fertility tracker (incl. app DaysyDay)
299.00 EUR

incl. VAT and Shipping - Product available - Delivery time: 2-3 days*

Daysy is an intelligent fertility tracker that lets you get to know your very own menstrual cycle.

Early pregnancy test at a bargain price? Better not

After ovulation, women who want to have children naturally want to know early on whether things have worked out. Theoretically, you could use leftover LH tests as an oracle in this case. These remain permanently positive if conception has taken place - the pregnancy hormone HcG is very similar to LH. After a few days of positive LH tests after ovulation, an early pregnancy is indicated4,5.

However,This oracle is unfortunately inaccurate. In addition, there is the risk that you also run with an early pregnancy test: The LH test may still be positive after your body has already decided not to continue the pregnancy. Because there was something wrong with the embryo or because the implantation went wrong ... there are many reasons this can happen. This can cause distress  after a positive LH testand the assumed joy of it.

If you are prepared for this, you can certainly try out LH tests. But you could also wait a few days longer - at no extra cost - and then use cycle trackers like Daysy to see how likely it is that you are expecting a baby. With Daysyall three lights light up simultaneously at the end of the cycle to indicate an early pregnancy. If, as expected, you don't have your period, the chance of a pregnancy  is much higher than a week earlier.

Whether you want to plan a pregnancy or are hoping togain a better understanding of your body: you can choose to use LH testing for this without much cost or effort. But it is best to not expect too much from it. And if you find that your values are permanently too high or too low: consult with your doctor

Daysy - Your personal fertility tracker (incl. app DaysyDay)
299.00 EUR

incl. VAT and Shipping - Product available - Delivery time: 2-3 days*

Daysy is an intelligent fertility tracker that lets you get to know your very own menstrual cycle.


  1. https://www.apotheken-umschau.de/diagnose/laborwerte/lh-luteinisierendes-hormon-ausloeser-des-eisprungs-740769.html
  2. https://www.frauenaerzte-im-netz.de/familienplanung-verhuetung/natuerliche-familienplanung/fruchtbare-tage-selbst-bestimmen-methoden/
  3. https://www.dr-nabielek.de/gynaekologie/kinderwunsch/ovulationstest
  4. www.mynfp.de/ovulationstests
  5. https://www.netdoktor.de/kinderwunsch/ovulationstest/