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Do pregnancy tests stop working after you're a certain amount of weeks?

(64 Posts)
Jadexclark Sat 27-Sep-14 16:40:43

Hi there, I was reading on the Internet that you can get a false negative if you've tested too late in your pregnancy because the tests only have a certain amount of HCG they pick up on.

How true is this? Thank you smile

Metalhead Sat 27-Sep-14 17:24:37

In the nicest possible way OP, the only way you'll get a definitive answer whether you're pregnant or not is by going to see your GP and getting a blood test as other people have suggested on your other threads. No matter how many different threads you start on this topic, the outcome will be the same. So just make an appointment on Monday and then you'll know for sure. Good luck anyway!

Jadexclark Sat 27-Sep-14 17:39:08

Metalhead, I was merely curious. I know I have to go to the doctors on Monday, but as it's the weekend, I'm trying to find solace in other ladies who are like minded and in the same situation! I'm too impatient, ha

Melodygrace Sat 27-Sep-14 18:16:51

I took a pregnancy test 5 days overdue my due date. Very positive. I did the test to see if it would show negative. So for me it wasn't true! And I like doing pregnancy tests for experimental purposes.

willitbe Sat 27-Sep-14 18:50:11

Yes it is called the "hook effect", where the levels of hcg are so high that then effectively overload the test and it gives a false negative. It can occur as soon as around 8 weeks pregnant, but is unusual.

Diluting the urine, will produce a positive test if this is the case. I believe that it is a dilution of around 10:1 that can do the trick.

It is also (although very rare) possible to be pregnant with a negative test due to your body not metabolising the hcg into your urine in the normal way, which again would give you a false negative.

As you have already been advised, go to your GP, your gp will feel your stomach and be able to tell if your uterus is enlarged, and then be able to send you for a scan if necessary. I hope you get an appointment soon to find out if you are pregnant or not.

DinoSnores Sat 27-Sep-14 19:09:33

As willitbe has nicely explained, the whole "HCG levels are too low in late pregnancy to cause a BFP" is a myth.

Very, very rarely, you can get a BFN and still be pregnant either because of the way your body processes HCG or because of the 'hook effect'.

Urinary pregnancy tests tend to show up as positive at levels of HCG greater than 10-25mIU/mL (depending on the make). As you can see on the table in the Wikipedia article, even at term, you'd expect HCG levels of 3,640 – 117,000mIU/mL, with the peak HCG levels happening at around 9-12 weeks. the point at which the hook effect is most likely as levels can be so very high.

Jadexclark Sat 27-Sep-14 21:53:37

willitbe, I really really hope it's the hook effect! I'll definitely do the diluting the urine thing, to see whether that brings up a positive or not. I feel bloated - and it's hard above my public bone. So I really don't know.

Dino, so you don't believe in the hook effect? It does seem likely, as I have so many Symptoms!

DinoSnores Sun 28-Sep-14 08:49:36

I'm a biochemist, of course I believe in the hook effect, but we see it very, very, very rarely. I think you need to see a doctor for a proper assessment.

Jadexclark Sun 28-Sep-14 08:52:45

I've just read your post back Dino, and I misinterpreted wrong yesterday.

I had no more tests to do the diluted urine with, so I took an OPK just on a whim because I've also read that they can test positive. I got a positive on the OPK - does that mean anything or not?

littlecrumb Sun 28-Sep-14 10:50:55

I heard that an opk can pick up if you are pregnant but I don't know how accurate that is.

KittyVonCatsington Sun 28-Sep-14 10:57:27

With the OPK thing, you can get positive OPKs at various different points in your cycle, so no, it is unlikely to mean you are pregnant.
It is just that usually, we stop testing with OPKs after the 'first' time of getting it-usually around ovulation. We can also get positive OPKs just before AF arrives, for example.
If anything, based on this post and your previous ones, you may have been experiencing an annovulatory cycle hence the length, and you might be about to ovulate, hence the hard sensation above your pubic bone. You have also been under a lot of stress with your relationship (poor thing) so this is likely to be causing your lack of AF.

You may have read some people will get positive OPKs when they are pregnant, but you would also have to get strong positives on a home pregnancy test as well, for this to be true, sorry.

I hope you get the answers you want at your GP tomorrow.

DinoSnores Sun 28-Sep-14 14:20:06

If the OPK was positive because of high levels of HCG (HCG is a very similar molecule to LH, the chemical that an OPK measures), I'd really expect the levels of HCG in your urine to be sufficiently high to show up on a pregnancy test.

Do let us know how you get on.

Jadexclark Sun 28-Sep-14 14:32:28

I've just took a pregnancy test, an IC one I got off a friend, and it came up positive I think!!!! What do you think Dino, Kitty and littlecrumbs?

KittyVonCatsington Sun 28-Sep-14 15:50:01

Oh sweetie, that stick is flooded. That means it is invalid as the urine escaped over the max line sad Sorry. You might have to try again xxxx

KittyVonCatsington Sun 28-Sep-14 15:53:29

A positive line will be much closer to the test line with the rest of the 'window' white not pink xx

Jadexclark Sun 28-Sep-14 23:05:21

Oh damn it hahaha. I did another Internet cheapie, one I've had for about 8 weeks, one I found ransacking my room after I used up the test that my friend gave me, what about this one Kitty?

Jadexclark Sun 28-Sep-14 23:05:42

But wouldn't it be a lot darker if I was 10 weeks? :/

BertieBotts Sun 28-Sep-14 23:08:50

That one looks clearly positive to me. I don't know how dark it should be. Hope you get some answers at the docs - make sure they check everything is as it should be.

yellowrose2728 Sun 28-Sep-14 23:17:12

That does look positive smile

What makes you think you are 10 weeks? I would say (and only based on my experience) this is an early pregnancy

Congrats maybe in order though? thanks

SoonToBeSix Sun 28-Sep-14 23:21:09

It is positive but faint.

Jadexclark Sun 28-Sep-14 23:34:21

Bertie, thanks for answering... I'm not sure about how dark it should be either, but I know by 10 weeks you should get a definite positive. I've also read if you're 10 weeks the line might be faint because of all the hormones in your body, sometimes a test can get overloaded.. Not sure how true that is though!

Thank you yellowrose smile! Me and my partner split up end of July unfortunately, and I know my last proper menstrual period was 14th July so I counted forward from there.. I havent had intercourse since I've been with him, so... Thank you! I'm hoping a congrats is in order haha!

I'm going to the doctors tomorrow for definite results. If I can get past the bloody nosey receptionists we have at our practise! X

FruitbatAuntie Mon 29-Sep-14 00:02:36

Hook effect is possible but v unusual as others have said.

I took a test the day I went in to have DS, out of curiosity as I'd read that tests don't work after a certain point. It still came out positive.

KittyVonCatsington Mon 29-Sep-14 06:25:30

Jade is that second post/picture a ClearBlue OPK?

It doesn't look like a home pregnancy test to me, but I could be wrong. If it is an OPK-that isn't positive as the lines need to be both the same colour. If it is a pregnancy test then it is positive (what brand/type is it, just out of curiosity?)

Good luck today at the doctors.

Jadexclark Mon 29-Sep-14 09:15:23

It's one I found on the internet about two months ago Kitty, I'm not sure what brand it is but it said that they distribute to NHS?

Rang the doctors and they don't have an appointment til Friday! I'm disgusted! I told them all about my situation as well...

Jadexclark Mon 29-Sep-14 09:30:34

It was these Kitty x

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