The Real Meaning of Beta hCG Levels

13 Jul
Beta hCG Pregnancy Test

Certainly the most anticipated lab test in a fertility clinic is a human chorionic gonadotropin (hCG) level. While everyone knows that having a positive beta hCG is the ultimate prize, it is far more difficult to truly understand what the test is really telling you.

First, what does a positive (+) beta hCG test really mean? Here we must differentiate between a urine test and a blood pregnancy test. The only real difference is the sensitivity of the test, meaning how high does the hCG level actually have to be to get detected. On a home pregnancy test, the lowest level routinely detected varies between 20-30 mIU/ml. As these levels are achieved fairly early in pregnancy – in fact by the time the expected period is missed – the levels should be above this detection level.

A blood test, on the other hand, is a more vigorous tool and can detect hCG very accurately as low as 5 mIU/ml. Levels below 5 can be detected, but the accuracy of these evaluations suffers greatly. These levels can be detected even before the missed period, hence their usage in IVF cycles. One thing that must be understood here is that these tests cannot distinguish between hCG created by the pregnancy or that given by injection. One must therefore be careful interpreting levels that have been drawn close to the time of the hCG trigger of ovulation/maturity. Twelve days is generally enough time to allow what was injected to be completely metabolized and cleared.

Second, how high must the beta hCG level be before we can actually expect to see something on ultrasound? Once upon a time, when the world was young and I was fresh out of training, we did primarily abdominal scanning. The hCG level most commensurate with seeing the pregnancy was very high, about 6500 mIU/ml. Since the advent of the trans vaginal probe and the great increase in the ability to see things in the uterus, this “U/S detectable” level decreases to about 1000 mIU/ml. This can be equated to about 6 weeks gestation (remember, we always add two weeks to go all the way back to the start of the cycle, not from the time of implantation).

Beta hCG Levels

The hardest question to answer is how fast these levels should increase. A common rule of thumb is that on average they should approximately double every two days. But remember that these are averages. When following such numbers, we must use curves like the one shown above. The only truly abnormal parts of the curve are the upper 2.5% and the lower 2.5%. All the other values strung between these two points are still normal, they are simply more or less than their neighbor. It is the same with hCG levels. If the number is not doubling, that is not a reason to “hang crepe” and panic. It is still most probably normal.

Additionally, the doubling time (time needed for the value to double) also changes as the pregnancy advances, hence you can expect the increase to slow down as you follow it. In fact, once the thresholds for ultrasound detection have been passed, following serial hCG levels does little except overly worry people. Again if I had a nickel for every baby I have held in my arms that did not initially have perfectly doubling hCG levels or for every D & C I have had to perform for a failed pregnancy that was indeed doubling, I would be retired in the South of France reading poetry and eating peeled grapes. At a bottom line, do not hesitate to ask your coordinator or physician about their ideas concerning these levels so you do not unduly worry yourselves.

1,151 Comments

  • Jessica says:

    Hi Dr Sher. Following my first IVF, I recently found out I am pregnant. My first beta at 14dpo was 125. Around this time I developed mild OHSS, which resolved in about a week. Unfortunately, my beta HCG results did not double as expected. My results were as follows:

    Beta #1 (14dpo) – 125
    Beta #2 (16dpo) – 213 (70% increase in 2 days)
    Beta #3 (19dpo) – 327 (33% increase in 2 days, 54% increase in 3 days)
    Beta #4 (21dpo) – 428 (31% increase in 2 days)
    Beta #5 (23 dpo) – 571 (33% increase in 2 days)

    At this time, my RE told me to stop all hormonal supports and prepare for a miscarriage . I did (which was devastating) and then returned on Monday for another HCG, expecting my numbers to decrease. Instead, these were my results:

    Beta #6 (26dpo) – 1199 (64% increase in 2 days, 110% increase in 3 days)
    Beta #7 (28dpo) – 2360 (97% increase in 2 days)

    On the day of my 7th beta, I also had my first ultra sound (6 weeks 0 days) and we saw the emrbyo in my uterus (ruling out ectopic) and a heartbeat. Despite stopping all supports a week ago, my estrogen and progesterone are both also “off the charts.”

    What do you think is going on? My RE doesn’t know what to think, and says there is not enough research out there on situations like mine. We don’t plan to do any further testing until my clinic reopens after the holidays. After that, we will do another ultrasound to see if the baby is still growing (I will be 9 weeks at that point). I really don’t know what to think or feel over the next 3 weeks while I wait. Obviously I want to be hopeful but I also don’t want to get my hopes up again if I am likely going to miscarry in the future (which I know is a strong possibility given my HCG history). I am hoping you have seen cases like this before and could share your thoughts/opinions.

    Thanks in advance.

    • Geoffrey Sher says:

      What probably happened is you started off with 2 implanting and one has absorbed with the other (hopefully proceeding normally.

      Hopefully a great Xmas present.

      Good luck!

      Geoff Sher

      • Jessica says:

        Hi Dr. Sher, thank you so much for the quick reply. I wish that was the case for us, but I really don’t think it was a vanishing twin, as I only had one embryo transfered. Any other thoughts?

        • Geoffrey Sher says:

          Either way…the pregnancy is surviving it would seem.

          Good luck!

          Geoff Sher

          • Jessica says:

            Thank you for your thoughts and your good wishes. I am so hopeful that the pregnancy will go on to survive. However, it seems all the stories I have read online of situations like mine (there are not very many, and obviously not all the variables are the same) go on to miscarry. Have you ever known a patient to have an HCG profile like this (with a single embryo transfer) and go on to have a healthy pregnancy?

          • Geoffrey Sher says:

            Yes I have…but only time will tell in your case.

            Geoff Sher

          • Jessica says:

            Thanks again for taking the time to share your thoughts, I appreciate it. Have a happy holidays!

          • Geoffrey Sher says:

            Same to you Jessica!

            Geoff Sher

  • Luna says:

    Hi! Just found out I am pregnant as a result of my first iui. I had a beta at 13dpo and the result was 62. The second beta, 48 hours later, was 87. Didn’t double. Everything else is great- high level of progesterone at 44 and estrogen at 315. I am having another beta tomorrow ( another 48 hours). Do you believe there is still hope?

    • Geoffrey Sher says:

      The slow rising beta hCG could be an ominous sign..but yes, there is still hope.

      Good luck!

      Geoff Sher

      • Luna says:

        Thank you so much for your reply! I just got the result of the third beta. It went up to 219! I guess my first one was a low rise. This is good news right? Pregnancy has a chance? Thank a million!

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