Test Overview

Home pregnancy tests can find the presence of a
pregnancy
hormone (called human chorionic gonadotropin, or hCG)
in a sample of urine. High levels of hCG are made during pregnancy. The home
tests have similar results to the pregnancy tests done on urine in most doctors’ offices if they are used exactly as instructed.

When a woman becomes pregnant, the egg is generally fertilized by a sperm
cell in a
fallopian tube (conception). Within 9 days after
fertilization, the egg moves down the fallopian tube
into the uterus and attaches (implants) to the wall of the uterus. When the
fertilized egg implants, the
placenta starts to develop and begins to release hCG
into the woman’s blood. Some of this hCG also passes in her urine. In the first
few weeks of pregnancy, the amount of hCG in the urine gets higher very
quickly-it doubles every 2 to 3 days.

There are two basic types of
home pregnancy tests.

  • The most common types of home pregnancy tests
    use a test strip or dipstick that you hold in the urine stream or dip into a
    sample of urine. An area on the end of the dipstick or test strip changes color
    if hCG is present, meaning you are pregnant.
  • A second type uses a
    urine collection cup with a test device. To use this type of test, you may
    place several drops of urine into a well in the test device or you put the test
    device into urine collected in a cup. An area of the device changes color if
    hCG is present, meaning you are pregnant.

The first urine of the morning (that has collected in the
bladder overnight) is the best one to use and has the most accurate test
results.

The accuracy of home pregnancy tests is different for
every woman because:

  • The days of a woman’s menstrual cycle and
    ovulation can change each month.
  • The exact day of implantation of
    the fertilized egg is not always known.
  • Each home pregnancy test
    kit has a different sensitivity to find hCG. If the level is very low, the
    first urine of the morning is the most likely to show a positive result.

While a few home pregnancy tests may be sensitive enough to
show a pregnancy on the first day of a woman’s missed period, most test kits
are more accurate about a week after a missed period.

Why It Is Done

A
home pregnancy test is done to detect pregnancy by
detecting human chorionic gonadotropin (hCG) in your urine.

How To Prepare

Equipment

You can buy home pregnancy test kits
at the drugstore or grocery store. You don’t need a prescription.

The
test kits generally have plastic dipsticks or test strips and instructions that
explain how to do the test. Some kits have a urine collection cup and a
dipstick that you dip in urine. Midstream kits have a test strip that you hold
in your stream of urine for several seconds. All kits tell you to wait a
specific amount of time before reading the results.

When to test

Home pregnancy kits can be used on
the first day of a missed menstrual period. But the test results are more
accurate if you wait a few days longer. If you do the test as soon as you have
missed a period and the results show you are not pregnant (negative results),
repeat the test in 1 week if your menstrual period has not started, or have a
pregnancy test done at your doctor’s office or a clinic.

General instructions

For any home test, you should
follow some general guidelines:

  • Check the expiration date on the package. Do
    not use a test kit after its expiration date-the chemicals in the kit may not
    work correctly after that date.
  • Store the test kits as directed.
    Many kits need to be stored in a refrigerator or cool place.
  • Read
    the instructions that come with your test carefully and thoroughly before doing
    the test. Look for any special preparations you need to take before doing the
    test, such as avoiding certain foods or limiting your physical
    activity.
  • Follow the directions exactly. Do all the steps, in
    order, without skipping any of them.
  • If a step in the test needs to
    be timed, use a clock. Do not guess at the timing.
  • Many home kits
    show color changes on a test strip. If you are color blind or have trouble
    seeing different colors, have someone else read the test results for
    you.
  • Record the results of the test so you can discuss them with
    your health professional.

How It Is Done

Carefully read the instructions that
come with the home kit. Instructions vary from kit to kit. Be sure to read the
result at the appropriate time indicated in the instructions for accurate
results.

If you have a kit that asks for a morning urine sample,
test urine that has been in the bladder for at least 4 hours. A first morning
urine sample (that has collected in the bladder overnight) gives the most
accurate test results. Test the urine within 15 minutes of collecting the
sample.

If you are using a midstream kit, urinate a small amount
first and then hold the dipstick in your urine stream as you finish urinating.
Test the urine sample according to the directions included in the test kit
package.

Specific instructions

  • Dipstick test. For a dipstick test, you place the
    end of the dipstick or test strip into a sample of urine. You will either
    urinate directly onto the labeled end of the stick for 5 to 10 seconds or put
    the stick into urine in a collection cup. If you are pregnant, a positive
    result (a color change or a symbol showing) will appear in that area of the
    dipstick or test strip.
  • Collection cup test. For a test that uses a
    collection cup, you urinate into the cup included with the kit and then collect
    several drops of the urine with a dropper or syringe. Place 5 or 6 drops of
    urine directly onto a test disk to complete the test. If you are pregnant, a
    positive result will appear in a special area on the disk as a color
    change.

How It Feels

There is no pain or discomfort in doing
a home pregnancy test.

Risks

There are no problems with collecting a urine
sample for a home pregnancy test. But there may be a chance that you read the
results wrong. With any home pregnancy test, if the test shows you are pregnant
(positive test), you should see your health professional to confirm the test
and arrange follow-up care. If the test does not show you are pregnant
(negative test), it is still possible that you may actually be pregnant. You
should repeat the test in 1 week if your menstrual period has not started. If
the repeat test is negative, probably you are not pregnant, but you should talk
to your health professional about why you are not having periods.

Results

Home pregnancy tests can find the
presence of a pregnancy
hormone (called human chorionic gonadotropin, or hCG)
in a sample of urine. If you are pregnant, most tests show a color change or a
symbol shows in the indicator area of the test strip or on the part of the test
device.

What Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include:

  • Taking the test very early in your pregnancy.
    HCG may not be found. In this case, the test kit may show that you are not
    pregnant when you really are pregnant. This is called a
    false-negative result. If you have drunk a lot of
    fluid, your urine may be diluted and this may also cause a false-negative
    result.
  • Certain things may cause the
    test results to show that you are pregnant when you are not pregnant. This is
    called a
    false-positive result. False-positive results may be caused by reading the test at the wrong time, letting the test equipment get
    warm, having protein or blood in the urine, or having hCG hormone in the urine
    from some other cause.
  • Taking certain medicines, such as chlorpromazine
    or methadone.
  • Taking fertility medicines that contain human chorionic
    gonadotropin.
  • Not reading the result at the right time as shown on
    the instructions. If you read the result too early or too late, the color
    change may not be accurate, and you will need to retest.

What To Think About

  • Some home pregnancy tests are easier to use and
    read than others. Be sure to follow the instructions exactly for accurate
    results.
  • Human chorionic gonadotropin (hCG) can be found in the
    blood before it can be found in the urine. A blood test can confirm a pregnancy
    about 6 days after the fertilized egg implants into the uterus (even before a
    missed menstrual period). To learn more, see the topic
    Human Chorionic Gonadotropin (hCG).
  • Many
    women are able to tell if they are pregnant simply by knowing their body has
    changed. A missed menstrual period, breast tenderness, morning nausea, and
    fatigue may be early signs of pregnancy. But a home pregnancy test can
    confirm pregnancy when a menstrual period is late.
  • Some health
    professionals may want to do another pregnancy test in their labs to
    confirm the pregnancy before beginning prenatal care.
  • If you are
    thinking of becoming pregnant, think about making changes in your nutrition
    (such as avoiding alcohol and taking a vitamin containing
    folic acid) to lower the chance of birth defects. Good
    nutrition before and during your pregnancy helps your health and the health of
    your baby.
  • If you are thinking of becoming pregnant, try to find
    your most fertile time (ovulation). This can be checked in several ways. To learn more, see the topic
    Fertility Awareness.
    Ovulation test kits may help you
    know your most fertile time. These are available without a prescription in
    supermarkets and pharmacies.
  • Confirming your pregnancy early can be
    very useful. It allows you to start prenatal care during the first month of
    pregnancy. Or, if the pregnancy is unplanned, you can talk with your health
    professional about other choices.

Common questions about home pregnancy tests

  • Why did I see a faint positive line an hour
    after I did the test?
    You may be pregnant but your hCG level may not be high
    enough in your urine. Take another test in a few days or talk to your health
    professional about a blood test.
  • Why was my test positive right
    before I started my menstrual cycle?
    You need to have a blood hCG test to check
    for other causes of a high hCG level.
  • Can I be pregnant but get a
    negative test?
    Yes, most women will get a positive test within a few days of
    missing their menstrual period but some women may get a negative test early in
    their pregnancy.
  • Can alcohol or drugs change the test? Most test
    results are not affected by alcohol or drugs, but you should not use these
    substances if you want to become pregnant or think you may be pregnant.

References

Other Works Consulted

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

Credits

ByHealthwise Staff
Primary Medical Reviewer Sarah Marshall, MD – Family Medicine
Adam Husney, MD – Family Medicine
Kathleen Romito, MD – Family Medicine
Specialist Medical Reviewer Siobhan M. Dolan, MD, MPH – Reproductive Genetics
Rebecca Sue Uranga, MD – Obstetrics and Gynecology

Current as ofMarch 16, 2017