Facts you should know about pregnancy tests

*Facts you should know about pregnancy tests medically edited by: Charles Patrick Davis, MD, PhD
- Pregnancy tests work by detecting a hormone in a woman's blood or urine: hCG (human chorionic gonadotropin) is produced when an egg implanted in the uterus.
- There are two types of pregnancy tests, one uses blood and the other uses urine (home tests); a quantitative blood test detects hCG earlier than a qualitative blood or urine test.
- Most home pregnancy tests detect hCG in a urine stream when, after a few minutes, a line or symbol appears if the test is positive (indicating pregnancy); most urine pregnancy test instructions urge a second test in a few days no matter what were the first results; follow package instructions – if a control indicator does not appear, the test result should not be trusted.
- Home tests are accurate, some better (more sensitive in showing early pregnancy) than others.
- Home pregnancy tests may test positive on the first day of a missed period, but almost all detect pregnancy 1 week after a missed period.
- Call your doctor for an appointment if you test positive for pregnancy with a home test.
- It is possible to be pregnant and have a negative home pregnancy test; that is why you should wait about a week to repeat the test. Most medicines and other compounds (alcohol, drugs) do not interfere with pregnancy tests; however, any drug containing hCG (some fertility drugs) may give false test results.
- Any questions or problems with pregnancy tests should be discussed with your doctor.
How soon can I use a home pregnancy test?
Some home pregnancy tests are more sensitive than others and can be taken before your missed period. But you may get more accurate results if you wait until after the first day of your missed period.
This is because the amount of the pregnancy hormone, called human chorionic gonadotropin, or hCG, in your urine increases with time. The earlier you take the test, the harder it is for the test to detect the hCG.
hCG is made when a fertilized egg implants in the uterus. This usually happens about 10 days after conception (when the man's sperm fertilizes the woman's egg).
My pregnancy test says I am pregnant. What should I do next?
If a home pregnancy test shows that you are pregnant, you should call your doctor to schedule an appointment.
Your doctor can use a blood test to tell for sure whether you are pregnant. Seeing your doctor early in your pregnancy also means you can begin prenatal care to help you and your baby stay healthy.
My pregnancy test says I am not pregnant. Could I still be pregnant?
Yes, it is possible you could still be pregnant. It's possible to be pregnant and to have a pregnancy test show that you are not pregnant.
The accuracy of home pregnancy test results varies from woman to woman because:
- Each woman ovulates at a different time in her menstrual cycle.
- The fertilized egg can implant in a woman's uterus at different times.
- Sometimes women get false-negative results when they test too early in the pregnancy. False negative means the test says you are not pregnant when you are.
- Problems with the pregnancy can affect the amount of hCG in the urine.
If a test says you are not pregnant, take another pregnancy test in a few days. If you are pregnant, your hCG levels should double every 48 hours. If you think you are pregnant but more tests say you are not, call your doctor.

SLIDESHOW
Boost Your Fertility: Ovulation Calculator, Pregnancy Planning and More See SlideshowWhat if I can't tell whether my pregnancy test is positive or negative?
Sometimes it can be hard to tell whether the test is positive or negative. The line may be faint, or you may worry whether you peed too much or too little on the stick. No matter how faint the line or plus sign, if you see it, you are most likely pregnant. The faintness of the line can mean you are early in your pregnancy and your hCG levels are still low. Also, the pregnancy test should have a control line that tells you whether the test was done correctly. If the control line is blank, then the test did not work and you should take another test.
What should I consider when buying a pregnancy test?
- Cost. Home pregnancy tests come in many different types. Most stores sell them over the counter (without a doctor's prescription). The cost varies depending on the brand and how many tests come in the box.
- Accuracy. Most tests can be taken as soon as you miss your period. Some newer, more expensive tests say they can be used 4 or 5 days before your period. Even so, they claim the best accuracy only after the date of your expected period.
What are the different types of pregnancy tests?
Pregnancy tests check for the hCG hormone in two ways:
- Urine test. This type of pregnancy test can be done at home or at a doctor's office.
- Blood test. This type of pregnancy test can only be done at a doctor's office. It takes longer than a urine test to get results, but it can detect a pregnancy earlier than a urine test (about 10 days after conception, compared to typically 2 weeks or more for a urine test). Your doctor may use one or both types of blood tests:
- A quantitative blood test (also called a beta hCG test) that measures the exact amount of hCG in your blood. It can find even tiny amounts of hCG. It can also tell you and your doctor how many weeks you are pregnant.
- A qualitative hCG blood test checks to see whether the pregnancy hormone is present or not. The qualitative hCG blood test is about as accurate as a urine test.
Latest Pregnancy News
Daily Health News
How do I use a home pregnancy test?
All home pregnancy tests come with written instructions. Depending on the brand you buy, the instructions may vary:
- You hold a stick in your urine stream.
- You pee into a cup and dip the stick into it.
- You pee into a cup and then use a dropper to put a few drops of the urine into a special container.
Different brands tell you to wait different amounts of time, although most are around 2 minutes. Depending on the brand of the test, you may see a line or a plus symbol, or the words "pregnant" or "not pregnant." A line or plus symbol, no matter how faint, means the result is positive.
Most tests also have a "control indicator" in the result window. This control line or symbol shows whether the test is working properly. If the control line or symbol does not appear, the test is not working properly.
Look for the toll-free phone number on the package to call in case of questions about use or results.
How accurate are home pregnancy tests?
Most home pregnancy tests claim to be up to 99% accurate. But the accuracy depends on:
- How you use them. Be sure to check the expiration date and follow the instructions. Wait up to 10 minutes after taking the test to check the results window. Research suggests that waiting 10 minutes will give the most accurate result.
- When you use them. The amount of hCG or pregnancy hormone in your urine increases with time. The earlier you take the test, the harder it is for the test to detect the hCG. Most home pregnancy tests can accurately detect pregnancy after a missed period. Also, testing your urine first thing in the morning can boost the accuracy.
- Who uses them. Each woman ovulates at a different time in her menstrual cycle. Plus, the fertilized egg can implant in a woman's uterus at different times. Your body makes hCG after implantation occurs. In up to 10% of women, implantation does not occur until after the first day of a missed period. This means home pregnancy tests can be accurate as soon as 1 day after a missed period for some women but not for others.
- The brand of test. Some home pregnancy tests are more sensitive than others. For that reason, some tests are better than others at detecting hCG early on. Talk to your pharmacist about which brand may be best for you.

QUESTION
The first sign of pregnancy is most often: See AnswerI have irregular periods and don't know when my next period will start. When should I take a pregnancy test?
Most pregnancy tests claim to be the most accurate after a missed period. But irregular periods can make it hard to predict when to take the test.
Periods are considered irregular if:
- The number of days between periods is either shorter than 21 days or longer than 35 days
- The number of days in the menstrual cycle varies from month to month. For example, your cycle may be 22 days one month and 33 days the next month.
If you have irregular periods, try counting 36 days from the start of your last menstrual cycle or four weeks from the time you had sex. At this point, if you are pregnant, your levels of hCG should be high enough to detect the pregnancy.
If your test says you are not pregnant, but you still think you may be pregnant, wait a few more days and take another pregnancy test. Or, call your doctor for a blood test.
Can anything affect home pregnancy test results?
Yes. If you take medicine with the pregnancy hormone hCG as an active ingredient, you may get a false-positive test result. A false positive is when a test says you are pregnant when you are not.
Some examples of medicines with hCG include certain medicines for infertility. If you are taking medicine to help you get pregnant, you may want to see your doctor for a pregnancy test.
Most medicines should not affect the results of a home pregnancy test. This includes over-the-counter and prescription medicines such as birth control and antibiotics. Also, alcohol and illegal drugs do not affect pregnancy test results.
How do pregnancy tests work?
All pregnancy tests work by detecting the pregnancy hormone, hCG, in the urine or blood. This hormone is present only when a woman is pregnant. If the pregnancy test detects hCG, it will say you are pregnant.
hCG is made when a fertilized egg implants in the uterus. This usually happens about 10 days after conception (when the man's sperm fertilizes the woman's egg). The amount of hCG builds up quickly in your body with each passing day you are pregnant.
So if you take a home pregnancy test too soon after implantation, your hCG level may not be high enough to detect the pregnancy. If the test says you are not pregnant, take another pregnancy test in a few days.
Subscribe to MedicineNet's Pregnancy & Newborns Newsletter
By clicking "Submit," I agree to the MedicineNet Terms and Conditions and Privacy Policy. I also agree to receive emails from MedicineNet and I understand that I may opt out of MedicineNet subscriptions at any time.
Health Solutions From Our Sponsors
United States. Office on Women's Health. WomensHealth.gov. "Pregnancy Tests." Jan. 31, 2019. <https://www.womenshealth.gov/a-z-topics/pregnancy-tests>.
Top Pregnancy Test Related Articles
Cramps but No Period
Having cramps but no period can occur because of conditions other than your monthly menstrual cycle. They may feel like period cramps of the lower abdomen when you are not due for your period and produce no blood. These 12 diseases and conditions are examples of what can cause abdominal cramping when not on period.Pregnancy Symptoms
What are the early signs and symptoms of pregnancy? Can you know before your missed period? Read about nausea and vomiting (morning sickness), bloating, tender breasts, and more. Explore first trimester symptoms of pregnancy and learn what week pregnancy symptoms start.Am I Pregnant Quiz
What are early pregnancy symptoms? In some women, symptoms range from a missed period to feeling lightheaded. Others may experience typical "morning sickness" and food cravings. Could you be pregnant? Take the quiz!Ectopic Pregnancy (Tubal Pregnancy)
An ectopic pregnancy is a pregnancy located outside the inner lining of the uterus. The majority of ectopic pregnancies occur in the Fallopian tube. Signs and symptoms of an ectopic pregnancy may include abdominal pain, lack of menstrual period (amenorrhea), vaginal bleeding, fainting, dizziness, and low blood pressure.
Treatment options for an ectopic pregnancy include observation, medication, or surgery.
How Can You Tell if You're Pregnant if You Have Irregular Periods?
Learn the signs of pregnancy, what causes irregular periods, and when to see a doctor.Kidney Pain: Symptoms, Treatment, and Causes
Kidney pain has a variety of causes and symptoms. Infection, injury, trauma, bleeding disorders, kidney stones, and less common conditions may lead to kidney pain. Symptoms associated with kidney pain may include fever, vomiting, nausea, flank pain, and painful urination. Treatment of kidney pain depends on the cause of the pain.Menstruation (Menstrual Cycle)
Menstruation (menstrual cycle) is also referred to as a "period." When a woman menstruates, the lining of the uterus is shed. This shedding of the uterine linking is the menstrual blood flow. The average menstrual cycle is 28 days. There can be problems with a woman's period, including heavy bleeding, pain, or skipped periods. Causes of these problems may be amenorrhea (lack of a period), menstrual cramps (dysmenorrhea), or abnormal vaginal or uterine bleeding. There are a variety of situations in which a girl or woman should see a doctor about her menstrual cycle.Ovulation & Fertility
Boost fertility and increase your chances to conceive. Learn about ovulation calendars, diet, aging and other factors that can affect pregnancy.What Is a Pelvic Exam?
A pelvic exam is a routine exam for women. Physicians use a pelvic exam to look for conditions in particular organs of a woman's body including the genital organs, uterus, cervix, fallopian tubes, ovaries, bladder, and rectum. Pelvic exams can evaluate several conditions. Some of these conditions include sexually-transmitted infections, such as gonorrhea, syphilis, Trichomonas, human papillomavirus, and Chlamydia, bacterial vaginosis, yeast infections, urinary tract infections, abnormal uterine bleeding, fibroid tumors, ovarian cysts, infertility, polycystic ovary syndrome, rectal bleeding, and endometriosis.PMS vs. Pregnancy (Differences and Similarities)
Many women have difficulty figuring out if they are pregnant, have PMS, or are about to start their period. The most common signs and symptoms of early pregnancy, PMS, and the start of your period include mood swings, back pain, increased urination, and tender breasts. These three conditions also share other similar signs and symptoms, but there are unique differences between each. Moreover, there are symptoms that only occur if you are pregnant. Early pregnancy symptoms, PMS, and the start of the menstrual period all have common signs and symptoms like mood swings, back pain, and breast pain. Symptoms and signs between the three conditions that may seem similar, but are slightly different include the following: Pelvic or abdominal cramping before or during your menstrual period is normal; however, the cramping of early pregnancy is mild. If you are pregnant, nausea and vomiting, or morning sickness, is common. They are not common symptoms of PMS. Fatigue is common in both, but PMS usually goes away once your period begins. Food cravings or aversions to certain foods are common in both pregnancy and PMS, but if you are pregnant, the cravings or aversions to foods are more specific and intense. You may have spotting or bleeding if you are pregnant or suffering from PMS. When the embryo inserts itself into the uterus (implantation bleeding), you may mistake it as your menstrual period. However, implantation bleeding is much lighter (not enough to soak a pad or tampon) than the heaving bleeding experienced at the beginning of your period. Signs and symptoms that you may have only if you are pregnant include, implantation cramping and bleeding, a white, milky vaginal discharge, and your areolas or nipples darken. The only way to find out if you are pregnant is with a pregnancy test. Home pregnancy test kits are available without a prescription at pharmacies and most grocery stores. Contact a doctor or other health care professional if you think you may be pregnant.Pregnancy (Week by Week, Trimesters)
Signs and symptoms of pregnancy vary by stage (trimester). The earliest pregnancy symptom is typically a missed period, but others include breast swelling and tenderness, nausea and sometimes vomiting, fatigue, and bloating. Second trimester symptoms include backache, weight gain, itching, and possible stretch marks. Third trimester symptoms are additional weight gain, heartburn, hemorrhoids, swelling of the ankles, fingers, and face, breast tenderness, and trouble sleeping. Eating a healthy diet, getting a moderate amount of exercise, also are recommended for a healthy pregnancy. Information about the week by week growth of your baby in the womb are provided.Pregnancy Myths and Facts Quiz
Being pregnant is a delicate time for both mother and baby. Take this pregnancy myths and facts quiz to separate the myths and facts about being pregnant, and learn the truth behind healthy pregnancies!Early Pregnancy Symptoms and Signs
Pregnancy symptoms can vary from woman to woman, and not all women experience the same symptoms. When women do experience pregnancy symptoms they may include symptoms include missed menstrual period, mood changes, headaches, lower back pain, fatigue, nausea, breast tenderness, and heartburn. Signs and symptoms in late pregnancy include leg swelling and shortness of breath. Options for relief of pregnancy symptoms include exercise, diet, and other lifestyle changes.Stages of Pregnancy: Week by Week
See pictures on the various stages of pregnancy. See and learn what changes a woman's body goes through and view fetal images of how her baby grows during the 1st, 2nd and 3rd trimesters.What Is a Positive Beta hCG Level?
A positive beta human chorionic gonadotropin (hCG) level usually means that you are pregnant. Pregnancy tests detect the hCG hormone in the blood and urine. The beta hCG levels are also measured using a test known as quantitative hCG testing.Pregnant? Don't Eat This
Do you know which common foods may be risky during pregnancy? Learn which foods to avoid, while pregnant, such as queso dip, lunch meat, coffee and more.