How Long After Implantation Do hCG Levels Rise?

Written by Matt Murphy, DNP, RN, CEN, TCRN

Updated on July 5, 2023

• After fertilization, implantation is the most important next step in your pregnancy journey.
• The primary hormone in early pregnancy is hCG which prepares the uterus for embryo implantation.
• HCG concentrations rise through the first trimester and can be measured to see if the pregnancy is progressing normally.
• The best time to take a home pregnancy test is 1-2 weeks after your missed period.

A successful pregnancy is dependent on the healthy implantation of the fertilized embryo to the lining of the uterus. HCG (Human Chorionic Gonadotropin) is the hormone tested for in both blood and urine pregnancy tests. HCG is also responsible for preparing the uterine lining and sending signals to the rest of the body to support a healthy pregnancy.

Measuring hCG in the early part of pregnancy is the primary way to check if the fertilized embryo is on track for a healthy pregnancy. Find out how hCG is tested and how long after implantation hCG levels will rise.  

How Long After Implantation Does hCG Rise?

HCG levels can be measured in both a blood test and your urine. Because blood tests are better able to pick up small amounts of hCG, it can be detected in your blood earlier than in urine. A blood test can detect hCG as early as 11 days after conception.

Testing for hCG in your urine is how home pregnancy tests work. An at-home pregnancy test can detect hCG in your urine 12-15 days after ovulation for those people with the standard 28-day menstrual cycle.

How Accurate is a Home Test?

Urine pregnancy tests are not as sensitive as blood tests. Because of this, there is a chance of getting a false negative. This may happen if it is too soon after your missed period and the hCG levels have not had a chance to increase. In this case, a false negative means you might not get a positive result when in fact you are pregnant.

In a normal pregnancy, hCG levels will continue to rise, doubling about every 72 hours. HCG will rise through the first semester and will then start to decrease. 

When Is the Best Time to Take a Pregnancy Test?

The best time to take a pregnancy test depends on several things. It matters what kind of test you would be using and the regularity of your menstrual cycle. If we’re talking about a blood test, the timing of that would be up to the medical provider managing your care.

Home pregnancy tests are always urine pregnancy tests and are less sensitive than the blood test in detecting hCG. You may not get the most accurate results if you’re testing close to when you believe your missed period would be. 1 out of 5 women who are pregnant would not get a positive result on the first day of a missed period, according to the FDA.

Pregnancy tests can vary in how reliable they are, so you may want to test farther out from your missed period. The FDA recommends taking a urine pregnancy test 1-2 weeks after your missed period for the best chance of getting accurate results.

Implantation: What It Is and When It Occurs

Every pregnancy starts with fertilizing the egg and ultimately leads to the implantation of that fertilized egg in the uterus. The process has many different parts, so to understand more clearly, it may be helpful to define some important terms.

Ovulation: With every menstrual cycle, the woman will ovulate. During this part of the process the egg will move into tubes called fallopian tubes. The fallopian tubes carry the egg to the uterus in hopes of that egg being fertilized. Once ovulation begins, there is a 12-48 hour window for fertilization.

Fertilization: Fertilization happens in the fallopian tubes. It requires the man’s sperm to meet up with the egg. This is when conception truly begins.

Embryo: After the egg is fertilized, it is referred to as an embryo in its very early stages as it grows into more cells.

Implantation: Once the egg has been fertilized, it continues to move to the uterus. With all other parts of the menstrual cycle working properly, the inside of the uterus will be prepared for the egg to attach or implant. With the new egg implanted in the wall of the uterus, the cells begin to grow rapidly. Some cells turn into the baby and others build the placenta.

How Long Does Implantation Take?

Implantation may be the most important part of this process after fertilization. If all goes well, it should take somewhere between 6-10 days for implantation to occur. Besides allowing the fertilized egg to grow, implantation sends critical signals to the rest of your body.

Signals during implantation tell your body to start releasing essential hormones which protect the inside lining of the uterus and the fertilized egg. If fertilization had not happened, your body would have sent different hormone signals. These different signals would result in the beginning of your menstrual period.

Ectopic Pregnancies

An ectopic pregnancy is a problem that can sometimes occur during the implantation part of the process. An ectopic pregnancy is when the implantation occurs while the egg is still in the fallopian tube. This means the egg starts to grow in the wrong place where it can’t survive and can harm the mother.

If there is any possibility you are pregnant, or you have had a positive pregnancy test and you begin to experience lower abdominal pain, this could be a sign of ectopic pregnancy. Ectopic pregnancies are very dangerous and need immediate medical attention.

What is Implantation Bleeding?

Implantation bleeding is what we call a small amount of spotting or bleeding seen early in the pregnancy. Implantation bleeding most often occurs between 10-14 days following conception. It is common, and it does not mean there is a problem with the pregnancy. This type of bleeding is thought to be related to the egg attaching itself to the inside lining of the uterus.

What About Fertility Treatments?

If you’re using fertility treatments such as In Vitro Fertilization (IVF), the process of implantation isn’t all that different. During IVF, egg and sperm are collected and fertilization occurs outside the body in a lab. Once the egg is fertilized, the egg is put back in the woman’s body.

Once the fertilized egg is placed into the uterus, implantation occurs the same way it would if fertilization had occurred naturally. 

How Does Implantation Affect hCG?

HCG stands for Human Chorionic Gonadotropin and it is the primary pregnancy hormone of conception. HCG starts being made after the egg has been fertilized and increases noticeably after implantation.

One of the most important things hCG does in the early stages of pregnancy is support implantation. HCG helps implantation by making the wall of the uterus better able to accept the embryo. It does this by telling your body to produce more estrogen and progesterone while also telling your body to stop menstruating.

Once implantation is finished, hCG continues to be produced, mainly by the placenta, and increases steadily through the first 12 weeks. This makes hCG levels an important measure of how well pregnancy is progressing.

What Are Normal hCG Levels During Pregnancy?

HCG starts being produced after fertilization and hCG values will steadily increase through the first trimester. To confirm pregnancy, your doctor might run a blood test to look for the simple presence of hCG in your blood. This is sometimes referred to as a qualitative hCG test.

One way a doctor may check to see if your pregnancy is on the right track is to measure how much hCG is in your blood. The doctor would compare your results to the amount that would be expected. This is sometimes referred to as a quantitative hCG test because it quantifies how much hCG is in your blood.

In my clinical practice working as a nurse in the emergency department, we would often draw qualitative hCG lab specimens for female patients complaining of abdominal pain if they were of child bearing age. If the test came back positive, often congratulations were in order. What was also on the agenda would be a quantitative hCG test that would be evaluated along side the patient’s LMP. This would give us an idea if the pregnancy was progressing normally to that point.

For a quantitative hCG blood test, your results would be compared to the expected amounts of hCG since your last menstrual period (LMP).

What if hCG is Too High or Too Low?

Sometimes the hCG results are outside what we would consider the normal ranges. The values may be lower or higher than expected.

If the amount of hCG in your blood is lower than expected, it could mean:

• The embryo isn’t growing as we would expect it to.
• You may be experiencing an ectopic pregnancy.
• There is a possible problem with the placenta, like a molar pregnancy.
• The number of weeks thought to have passed since your LMP is not correct.

If the amount of hCG in your blood is higher than expected, it could mean:

• There may be more than one embryo implanting.
• There could possibly be a molar pregnancy.
• The number of weeks thought to have passed since your LMP is not correct.

If hCG is Abnormal, What Happens Next?

Knowing exactly why the hCG level is not within the expected range is only one piece of the puzzle. Determining the cause would need more information. Some medical providers may want to repeat the test in a couple of days. They may also want to send you for an ultrasound to gain more information.

The ultrasound looks for the location of the embryo to confirm successful implantation. Embryos that are not implanted properly, or are not in the right location, can be seen on ultrasound. This can possibly indicate an ectopic pregnancy or early miscarriage. 

The information WonderBaby provides is not intended to be, and does not constitute, medical or other health advice or diagnosis and should not be used as such. Always consult with a qualified medical professional about your specific circumstances.