How to use a pregnancy test correctly and when is the right time to use it【supervised by doctor】

Summary of this article

Pregnancy tests are an easy way to find out if you are pregnant at home, but the right timing and use are important to get accurate results. Early pregnancy is particularly important, as over-the-counter pregnancy tests are usually more than 99% accurate, with little difference in price and accuracy. It is appropriate to use a pregnancy test approximately one week after the expected start of menstruation, with morning urine being suitable for more accurate results. If the pregnancy test shows a positive result, it is always important to visit an obstetrician and gynaecologist for an accurate diagnosis.


What is the purpose of using a pregnancy test?

The original purpose of using a pregnancy test is not to establish whether or not you are pregnant, but to get an earlier result and seek medical attention. The early detection of a possible pregnancy with a simple, self-administered pregnancy test leads to a visit to an obstetrician/gynecologist and an accurate diagnosis. Particularly in early pregnancy, when the baby’s vital organs such as nerves and brain are being formed, you need to be more careful than ever about your lifestyle, hygiene and use of medicines. Once a medical examination is carried out and the pregnancy is confirmed, it is possible to start taking care of yourself appropriately as an expectant mother from an early stage.

Especially if you are considering NIPT or an amniotic fluid test after pregnancy, you should use a pregnancy test to confirm a positive pregnancy result. It is important to check the start of your menstrual period and the day of ovulation on a regular basis and use a pregnancy test to check for positive or negative results if there are any physical changes that raise suspicions of pregnancy, in order to avoid missing the right time for the test.

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What are the prices and accuracy of pregnancy tests of concern?

Pregnancy tests are readily available at drugstores. Pregnancy tests cost around JPY 300-2 000, depending on whether it is a one-time or two-time test and on the manufacturer.

For first-time users, it may be difficult to understand the price of pregnancy tests, the accuracy of the test and how pregnancy tests work. The following explains the accuracy of pregnancy tests and how pregnancy reactions work.

How pregnancy tests produce a pregnancy response

When a fertilised egg implants, a placenta is formed, in which the hormone hCG (human chorionic gonadotropic hormone) is produced. hCG can be detected in the blood and urine from the fourth week of pregnancy, when the period is due. Pregnancy tests confirm positive or negative pregnancy reactions by checking for the presence of hCG in the urine.

Pregnancy tests are more than 99% accurate when used correctly

Normally, hCG is not released in the urine unless a woman is pregnant. Therefore, if pregnancy tests are used correctly, the test results are extremely reliable, with an accuracy of more than 99%. The specific accuracy of each product is published and should be referred to when using it.

There is little difference in accuracy between over-the-counter pregnancy tests and hospital pregnancy tests. However, over-the-counter pregnancy tests are less expensive, while hospital pregnancy tests are slightly more expensive because they are not covered by insurance.

The accuracy of both over-the-counter and hospital pregnancy tests is the same, the only difference being the price. For these reasons, if you notice any physical changes that raise suspicions of pregnancy, you should first order a pregnancy test (kit) and carry out the test yourself.

How to use a pregnancy test correctly and when is the right time to use it【supervised by doctor】

What is the correct way to use a pregnancy test?

Over-the-counter pregnancy tests include instructions for use in the instruction manual and on the packaging. For most tests, there is no significant difference in the method.

How to use pregnancy tests

Pregnancy tests, hCG pregnancy tests, early pregnancy tests, determination tests, pregnancy test kits and other terms vary, but there is little difference in how they are used and how they work. Let’s take a step-by-step look at how to use common pregnancy tests.

Pouring urine on a pregnancy test

Apply urine to the designated area. The number of seconds to urinate may vary from product to product, so check the instruction manual in advance.

Level and wait until the decision is made

Place the pregnancy test in a horizontal position and wait for the result. If you place the test at an angle or vertically, you may not get a correct result. It is also important to secure the placement of the test before testing.

Most pregnancy test strips will show a sign that the test is over, so make sure that the test has been carried out correctly before picking up the strip.

③Check the results of the decision

Positive and negative signs vary from pregnancy test to pregnancy test, but in general, ‘a line in the decision window’ = positive = ‘high possibility of pregnancy’. On the other hand, if no line is seen in the test window, it is a negative result and it can be judged that the possibility of pregnancy is low.

To avoid misunderstandings or premature assumptions, it is recommended to read the instruction manual in advance to find out how many minutes it takes to reach a decision, how to perform the test correctly and how to read the decision result.


How to avoid mistakes with pregnancy tests?

Although accurate pregnancy tests are highly accurate, some may require a higher degree of accuracy. If so, the following points should be considered

Inspect as soon as you wake up in the morning

Basically, urine can be tested at any time of day, but urine immediately after waking up in the morning is considered to be more concentrated. The accompanying hCG concentration is also relatively high during the day, which makes it easier to obtain results.

If urine samples are taken, they should be tested at intervals of no more than a few hours

When testing with a urine collection rather than pouring urine, bacteria can grow in the urine if too much time has passed. Bacteria can also interfere with the accuracy of the pregnancy test, so do not wait too long after collecting the urine and test it immediately.

Be careful how you store pregnancy tests

Failure to store pregnancy tests properly may also result in incorrect test results. If you buy and store pregnancy tests at home for future pregnancies, it is important to keep them away from extremely hot or cold temperatures. Expired pregnancy tests should also be avoided as they may not give accurate results.

Positive or negative test result not known with a thin line in the decision window

When using a pregnancy test, a thin line (line) may appear in the decision window that is difficult to judge as positive or negative. The main causes may include the following

  • Too much water had diluted the concentration of urine
  • Pregnancy test used too early (flying test)
  • The fertilised egg did not implant completely and the pregnancy did not continue
  • Had recently experienced a miscarriage and still had hCG in the body
  • Hormone injections due to fertility treatment

Some people consider a thin line to be positive, but this is not always the case. It is also possible that the test result may have been affected by your own miscarriage experience or treatment situation. Even if you have no particular reason to think this is the case, it is better to arrange the testing environment and retest a few days later to be sure.

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Too early or too late! When do pregnancy tests react?

Although pregnancy tests boast a high accuracy rate of 99%, they may not react correctly, such as no line, if used too early or too late. It is important to find the right time to use the test to obtain more accurate test results.

The test kit does not react until after the expected start of menstruation

Pregnancy tests determine whether a woman is pregnant by measuring the amount of hCG in her urine. hCG is excreted in the urine from the fourth week of pregnancy, but it is not released in sufficient quantities for most tests to react correctly until the fifth week of pregnancy. Although it is understandable to want to know the result as soon as possible, it is advisable to use a pregnancy test around one week after the expected start of the period.

Over-the-counter pregnancy tests also specify when to use them, from when to when, so be sure to read them carefully.

What is an early pregnancy test?

If you want to know the result as soon as possible, one option is to use an early pregnancy test, which has a relatively high sensitivity for hCG. An early pregnancy test can confirm a positive or negative result 3-4 days before the expected start of menstruation if you are pregnant.

What is a flying pregnancy test?

If the pregnancy test is used too early, the amount of hCG secreted may not reach the prescribed level, resulting in a negative pregnancy test, a thin line that is difficult to determine, or no line. Many people who have failed to use a pregnancy test seem to have done a ‘flying test’ where they used the test too early. In order to get an accurate pregnancy test, do not be in a hurry and wait for the manufacturers’ recommended time of use.

What happens if the pregnancy test is used too late?

Pregnancy tests may not give an accurate result if too much hCG is produced. hCG production peaks around the 10th week of pregnancy, so if you use the test at this time, you may not get a correct result. It is important to know when your period is due to start, and if you notice that your period is delayed, do not miss the timing of the test.

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Can pregnancy test results be wrong?

Although highly accurate, pregnancy tests are still not 100% accurate. It is possible for a test result to be wrong even if it is used correctly.

Causes of false positive pregnancy tests

If a pregnancy test shows a positive result but the woman is not actually pregnant… the following are possible causes.

Overspraying urine

Applying too much urine to the pregnancy test can lead to false positives. Pregnancy tests cannot give a correct test if there is too little or too much urine on the pregnancy test. It is important to check the instructions for the pregnancy test beforehand.

High levels of protein and sugar in the urine

People with diabetes, for example, have high levels of sugar in their urine. Blood or protein may also be present in the urine due to diseases such as cystitis. In these cases, the test reagent may not react normally and a false positive result may be obtained.

Administering hCG injections for infertility treatment

Some people may be administered hCG injections as part of their fertility treatment. As the administered hCG remains in the body for a certain period of time, if a pregnancy test is used without a certain period of time after treatment, a positive result may be given regardless of whether or not pregnancy has occurred. If you are undergoing fertility treatment, consult your doctor and determine when to use the test kit.

Suffering from hCG-producing tumours

It is known that hCG secretion increases when a woman has lung, ovarian or cervical cancer. If you have such an hCG-producing tumour, you may also test positive with a pregnancy test.

It was a miscarriage

If a woman becomes pregnant once but has a miscarriage because the baby fails to develop, hCG remains in the body for a certain period of time. It is not uncommon for a woman to go to an obstetrician because of a positive pregnancy test, only to find that she has already had a miscarriage. False-positive results may occur in both cases of chemical and comorbid miscarriages.

It can be a shock to find out that you thought you were pregnant, but it was a false positive. It is important to bear in mind in advance that this can happen.


Causes of false negative pregnancy tests

On the other hand, if the test shows a negative result but the woman is in fact pregnant, what are the possible causes?

Inspection time is too early

If the pregnancy test is used too early, it is more likely that the hCG has not reached the reference level and a negative result will result. Again, be careful about the timing of the use of the test.

Thin urine concentration

When a large amount of water is consumed, the concentration of urine becomes thinner and the concentration of hCG is inevitably lower. If a pregnancy test is used at this time, the hCG level will be lower than the threshold value and a negative result may be given even if the woman is pregnant.

Pregnant with multiples

Pregnancy tests may not give normal results if the hCG concentration is too high. If a woman is pregnant with multiples, the hCG concentration tends to be higher, which may result in a negative result as a result of exceeding the upper limit of the test’s response.

Having an abnormal pregnancy

In the case of an abnormal pregnancy, such as an ectopic pregnancy, the increase in hCG secretion may be slow and a pregnancy test may not produce a positive result even if a pregnancy test is used at the right time.

Even after a negative result on a pregnancy test, the situation may continue to raise suspicions of pregnancy, for example, if the woman does not have her period or if she is not feeling well. If you are not sure about the negative result, wait at least three days after the first test and take another test.

Always go to an obstetrician or gynaecologist if you test positive

If the timing and usage are correct, pregnancy tests provide results with an infinitely high degree of accuracy. However, a positive result does not necessarily mean that the pregnancy is normal. If you get a positive result, see your health care provider as soon as possible and take another test.

NIPT at Hiro Clinic NIPT for a healthier pregnancy period

If you get a positive pregnancy test, seek medical attention as soon as possible. If the pregnancy is confirmed, why not consider NIPT for a healthier pregnancy and delivery?

NIPT can be performed using only a blood sample from the mother. Once the pregnancy has been confirmed by ultrasound, it is possible to check for chromosomal abnormalities in the foetus and possible risks of congenital diseases. The test is highly accurate, with a sensitivity and specificity of 99.9% for 21 trisomy (Down syndrome).

Fetal chromosomal abnormalities often have a significant impact on the mother, including the risk of miscarriage. If you have an older pregnancy or want to know the health status of your baby at an early stage, please contact Hiro Clinic NIPT for a consultation.

World-class NIPT
Experience unparalleled excellence in Non-Invasive Prenatal Testing (NIPT) at Hiro Clinic. Our world-class services blen...



Some frequently asked questions about pregnancy tests are listed below.

  • Q
    The line on the pregnancy test disappears within the time limit, or the line appears after the time limit.
    In some cases, a line appears in the pregnancy test window but disappears within about a minute. In this case, it is highly likely that as the urine soaks up the water, the area where the reagent was placed temporarily appears as a line, and the test result is considered negative.

    The other most common case is that the line appeared long after the decision time. Very low levels of hCG in the urine can cause such a result. It is possible that the pregnancy test was used too early, and the test should be repeated a few days later.
  • Q
    What is an 'evaporation line'?
    A faint line may appear in the decision window after some time has elapsed.

    This is thought to be due to the evaporation of water from the urine that has soaked into the pregnancy test, increasing its density and leaving behind a component in the urine, and is called an 'evaporation line'.

    If there is a blurred, thin grey line that is different from a positive test, the possibility of an evaporation line should be considered.

Article Editorial Supervisor

Dr Hiroshi Oka

Dr Hiroshi Oka

NIPT specialist clinic, MD

Graduated from Keio University, School of Medicine


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