I am an LPN (licensed practical nurse), and I am currently employed at a local hospital working in acute/transitional care.
Pregnancy tests attempt to determine whether or not a woman is pregnant. Markers are found in blood and urine, and pregnancy tests require sampling one of these substances. While this seems simple enough, not all pregnancy tests are of equal quality, and there are several things you should know about how pregnancy tests work before buying one.
What to Know About Pregnancy Tests
- Which tests work best and earliest?
- Should you use a pink or blue dye pregnancy test?
- What are some common types of pregnancy tests?
- Are digital tests less sensitive?
- Should you use an early pregnancy test?
- What causes a false positive in a pregnancy test?
These six questions will be answered in the paragraphs below. Pregnancy is complicated, but learning about how pregnancy tests work can teach you a lot about your body. Pregnancy testing can be a stressful process. This article aims to help put your mind at ease.
Which Pregnancy Tests Work the Earliest?
First Response digital and manual tests are the most sensitive tests on the market. They can detect hCG-h. This is the kind of hCG that women produce very early on in pregnancy. In fact, using these tests, you can find out up to six days prior to the date of your expected period whether or not you are pregnant. These tests are able to work so early because they detect hCG at 12.5 mlU/ml, and sometimes as low as 6.5 mIU/ml. First Response detected pregnancy hormone levels in 96% of pregnant women within 4 days before their expected period and in 99% of pregnant women within 3 days before their expected period.
Clearblue Easy and EPT are both less sensitive than First Response, but more sensitive than other tests on the market. The sensitivity of Clearblue Easy Earliest Results was measured at 25 mIU/mL. They have a pregnancy early detection success rate of about 80%. That said, First Response and Clearblue are not the only tests on the market.
Different Kinds of Pregnancy Tests
- Internet cheapies such as Wondfo are best for those who want to do a lot of testing and early testing. These tests are just as sensitive as the name brand tests; however, they will not break the bank.
- Digital pregnancy tests should not be used for early testing; however, they will take the guess-work out of reading the results. They are great for "confirming" a positive result or for use after a missed period.
- Pink dye pregnancy tests are better than blue dye pregnancy tests. Pink dye tests are usually easy to read and are less likely to give you a false-positive result or evaporation line.
How to Get the Most Accurate Results?
For the most accurate results, wait until you have missed a period before you test. However, this does not mean that you won't get a positive result before your missed period. A faint line is still a positive line. The lower the sensitivity (example: 20 hCG compared to 50 hCG), the earlier the test will detect a pregnancy.
How Soon Can You Take a Home Pregnancy Test?
Wait to take a pregnancy test until the week after your missed period. If you don't want to wait until you've missed your period, you should at least wait a few weeks until after you have had sex. If you're pregnant, your body needs time to develop detectable levels of hCG.
Should You Use a Pink or Blue Dye Pregnancy Test?
As if there is not enough to worry about already, you also need to make the decision whether you want to purchase a pink or a blue dye pregnancy test. What is the difference?
Most experienced pregnancy test users will tell you to avoid the blue dye tests if possible. The reason for this is that blue dye tests give a "false positive" or an "evaporation line" more often than pink dye tests do.
What Is an Evaporation Line?
An evaporation line on a pregnancy test is due to the evaporation of urine in the test window where the antibody strip is located. This will result in a colorless line that may be mistaken for a positive result. Usually, the evaporation line is more grey than pink or blue. It may appear like a shadow.
In order to prevent evaporation lines, follow the test instructions. Most pregnancy tests need to be read in five minutes or less. If the pregnancy test is interpreted later than five minutes, the second line may actually be an evaporation line rather than a positive result.
People also find blue dye pregnancy tests harder to read, especially with early testing. Testing before one's period is due can result in a very faint positive result. You may need to squint to see it and question whether it is actually there or not. Most people find that there is less guesswork when using the pink dye tests.
Pregnancy Test Sensitivity Levels
|Brand||Human Chorionic Gonadotrophin (hCG) Detected||Brand||Human Chorionic Gonadotrophin (hCG) Detected|
First Response Early Result
First Response Gold Digital
Answer Early Result
hCg One Step
hCG One Step Ultra
Clear Blue Easy Early Result
Clear Blue Easy Digital
New Choice/Dollar Store
Simplicity No Step
Fact Plus Pro
First Response 6 Days Sooner (rectangular window)
Common Types of Pregnancy Tests
Clear Blue Digital
$13 for 2, $18 for 5, $40 for 20
Clear Blue Digital with Conception Indicator
$16 for 3, $18 for 5, $40 for 20
$14 for 2, $19 for 3
First Response Gold Digital
$20 for 2, or $10/ea
|Pink Dye Tests||Price|
All First Response Tests (Early Result, Rapid Result)
$9 for 2, or about $5/ea
$8 for 2
$10 for 2
$9 for 20 pack of strips
$10 for 3
|Blue Dye Tests||Price|
$8 for 2
$13 for 3
$6 for 2
Are Digital Tests Less Sensitive?
The short answer is, yes. Digital tests are also quite often a little more expensive. Are they worth the extra money?
Digital pregnancy tests can be great because they take the guesswork out of things. There is no stressing about whether you see a second line or whether that second line is dark enough. They simply state "pregnant" or "not pregnant" and that's that.
However, digital pregnancy tests are not the greatest for those who like to test early (before your period is due) or for those who test often, as this can be quite expensive. On forums, it is not uncommon to see the question, "I have a faint positive line and a negative digital test. Am I pregnant or not!?"
Of course not all digital tests are less sensitive, but on average they will only pick up hCG levels of 50 or higher while line tests (on average) pick up an hCG level of 25 or higher.
Should You Use an Early Pregnancy Test?
Using an early pregnancy test is not only a bit of a gamble with your emotions, it can strain your wallet. The chances of getting a false negative are much higher when testing before your expected period rather than after you have missed a period.
How to Get the Best Results From Your Early Pregnancy Test
For the best results, wait at least until the day of your missed period before you test. This does not mean that you cannot get a positive result earlier than that. On average, after ovulation, it takes the fertilized egg approximately 6-12 days to implant into the uterus. It then takes a couple more days for it to start producing hCG at high enough levels to be detected by pregnancy tests. Remember, hCG usually doubles every 2-3 days, so if the test is not positive today that does not mean it won't be in two days.
What Is hCG and Why Is It Important?
hCG is a protein hormone that is produced in large amounts in early pregnancy. It is similar to luteinizing hormone (LH). hCG's primary role is to keep the corpus luteum functioning. The corpus luteum produces estrogen and progesterone which are important for a healthy pregnancy.
How Early Can I Get a Pregnancy Result?
The earliest you will get a positive pregnancy result is likely, but not always, nine days past ovulation. It depends on the test's sensitivity level. At this point, there is approximately a 50% chance that, if you are pregnant, your test will read positive (likely very faint). Most women receive positive pregnancy results between ten and sixteen days past ovulation; however, this does not mean that you can't get an accurate positive result earlier or later. It all depends on implantation and the sensitivity of the pregnancy test.
What Causes a False-Positive?
In rare cases, you can have a false-positive result. This means you're not pregnant but the test says you are. False-positives are the result of blood or protein being present in your urine. Certain drugs, such as tranquilizers, anti-convulsants, or hypnotics, may also cause false-positive results. If you suspect that you may have received a false-positive, it's best to take multiple tests spaced out over a few days.
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
Questions & Answers
Question: I had sex without a condom, and my partner never ejaculated to my knowledge. We had sex twice more with a condom, but after finishing the condom came off when he was pulling out. It has been a few days, and I should have started my period, but I have not. Is there a possibility that I'm pregnant, or is it just my nerves?
Answer: Any time you have unprotected sex there is a chance of pregnancy. However, stress could also be delaying your period. It's best to take a pregnancy test and see!
Question: I have had 2 periods since I gave birth on August 14th and I’m late by 3 days. I’m only breastfeeding. Could I be pregnant? Or I am having no period because of breastfeeding? I took a FFRP and got a faint and negative on a dollar tree test.
Answer: Sorry for the late response. Generally speaking a faint positive is still positive. I would suggest investing further.
If you are not pregnant. It is very possible for breastfeeding to cause you to have late or missed periods.
Question: I haven't gotten my period for two months. It's the end of the month, and now I'm bleeding. I don't know if it's my period or what. Should I see a doctor?
Answer: If you are still young, it is very common for your period to not be regular quite yet, which may result in skipping a period or two from time to time. If you have had unprotected sex in the past month or two, it is possible that you may be pregnant and this is either bleeding during your pregnancy or a miscarriage.
If you have not had unprotected in the past couple months, a trip to the doctor may not be necessary at this point (however, you know your body best!). If your period continues to be wonky, then I suggest a trip to your doctor.
If you have had unprotected sex then I would suggest seeing your doctor.
Question: I'm a week late on my period, but clear blue gave me a negative but the equate brand gave me a positive. What should I do with these conflicting pregnancy tests?
Answer: False positives basically don’t exist. So likely what happened was the Equate brand is more sensitive. Meaning it probably picks up on lower levels of the pregnancy hormone.
Question: I've had three kids in the last four years, so my body has been pretty weird, but I didn't get my period last month (not entirely rare for me). This month, I have been spotting for two weeks now. I have gotten a faint positive pregnancy test result, and I'm just kinda wondering what the bleeding was then? I've never had any bleeding before with my other three kids
Answer: The bleeding could mean a few things. I highly recommend seeing a doctor to have some blood tests. For some women, it’s normal to have some spotting here and there throughout their pregnancies, especially if it is around the time of your expected period. Or it could mean that your hormone levels are too low and your pregnancy is not viable.
Tracy B (author) from Canada on October 11, 2018:
Sometimes the blue dye pregnancy tests aren't as sensitive as the pink dye tests. You also may have used less concentrated urine for the second test.
I would say a line is a line. And that yes, you are pregnant. However, it is best to see your medical professional to confirm. Good luck!
Sarah smith petit on October 05, 2018:
I’ve had a dollar tree hcg pregnancy test and it was positive then i took clear blue test and it came out negative am I pregnant. I’m puking and my stomachs cramping any advice ?? My son is nine months and this feels different?