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Original poster

If you read your lateral flow test long after 30 mins

94 replies

Friedbanana · 15/03/2021 00:52

Does it show a very faint T line (positive result)? I feel like an idiot, I know I should have set a timer for 30 mins- I will next time. I feel really bad for wasting a test as I know I have to do another one now. But it was my first time doing the test and I checked after 25 mins and it showed negative. I then sat next to the test and started doing work on laptop, and got a bit absorbed and completely forgot to look again, until 1.5 hours after I’d taken the test. I will do another one before I go into work tomorrow, but I just wanted to ask if it’s normal for a very faint line to appear long after the test has been taken? It’s extremely extremely faint!

OP posts:
Original poster
Friedbanana · 15/03/2021 09:18

Thanks everyone! I did another one and checked right on 30 mins, it was negative. But then the same has happened, about 10 mins later, a very very faint line appeared. Which is odd, but it says on the website and instructions that if a positive result appears after 30 mins to not report as positive as the test is void after 30 mins, so I’m going to take it as a negative! Thanks for all your replies!

OP posts:
Moonme · 15/03/2021 09:21

Could you book a PCR just to be sure?

Howshouldibehave · 15/03/2021 09:31

@Friedbanana

Thanks everyone! I did another one and checked right on 30 mins, it was negative. But then the same has happened, about 10 mins later, a very very faint line appeared. Which is odd, but it says on the website and instructions that if a positive result appears after 30 mins to not report as positive as the test is void after 30 mins, so I’m going to take it as a negative! Thanks for all your replies!
Bizarre-I have been doing these for weeks and never got any strange lines. I think I’d be tempted to do a PCR to check.
cathyandclare · 15/03/2021 09:41

I had one turn positive the next morning, 12 hours later ( although may have changed earlier, I didn't look). I did a thread on here and was told it was invalid. I did two timed tests the next day and both were fine.

MRex · 15/03/2021 09:43

If you aren't sure, go for a PCR test. There are loads of slots and you'll most likely get the result early tomorrow.

Strangekindofwoman · 15/03/2021 09:43

They have to be read at 30 minutes and that is the result you use. In my experience a positive will show within the first 5 minutes.

Bufferingkisses · 15/03/2021 09:45

I agree, we've been doing our own for months and I have never seen a negative change to positive (obviously anecdata isn't fact) but I would be tempted to book a PCR in your situation.

HazelWitch · 15/03/2021 09:47

I think it is a positive.
If you leave a negative test (hours, days etc) it will not go positive.
The faint line is specifically mentioned in the instructions as being positive, even if faint.

Toddlerteaplease · 15/03/2021 10:48

I've not Noticed this. And I tend to do mine and forget about it.

VaccineYayVaccineNay · 15/03/2021 11:00

Both mine and DHs lateral flows were positive with a very faint line. Took nearly the full half hour to show up. Confirmed positive with PCR. My DS had a very strong positive line on his which came up in seconds. Other 2 children negative. The tests were on the bench for hours after and none of them changed.

ChittyChittyBoomBoom · 15/03/2021 11:49

My negative tests have never shown a faint positive after the 30 mins. I’d book a pcr test to be on the safe side as I think it’s strange that it’s happened twice now.

Comefromaway · 15/03/2021 13:02

My husband took his to work this morning 2 hours after he took it because the website where he has to register the results was glitching. It remained negative.

OverTheRainbow88 · 15/03/2021 13:10

I would second the pcr test as I’ve done about 5pf LFT and it’s never gone from negative to a positive after time.

OverTheRainbow88 · 15/03/2021 13:10

*50

FishWithoutABike · 22/03/2021 07:33

Did you do a pcr?

duffeldaisy · 22/03/2021 08:41

You’ve probably done a pcr by now anyway, but the website went to an error page yesterday when I tried to input a neg result, I got distracted and lost the test. Found it this morning under the sofa and there were no changes or extra lines, even though it’d been knocked upside down all night. I hope that helps!

ArriettyCArriettyC · 25/03/2021 14:17

@Friedbanana what was your outcome please? Was your PCR positive? We have exactly the same thing. LF test left overnight became positive in the morning, then two more subsequent ones were very faintly positive at just after 30 mins - maybe 40 mins or so. we have done PCRs this morning, fingers crossed please!

Laurafrancis · 21/05/2021 18:43

Did any of you saying this happened to a PCR?

Same position rn and wanting to know the result!

MereDintofPandiculation · 21/05/2021 20:52

I’ve got one I took last Tuesday. Still just the one line

GlutenFreeGingerCake · 21/05/2021 20:56

Agree I've kept mine and they never show a positive line

Glitterandunicorns · 15/06/2021 13:08

@Friedbanana can I ask what the outcome of your PCR test was please? I'm in the exact same position (very faint second lines on 2 lateral flow tests; one after 2 hours and one after about 45 mins).

I've ordered a PCR test but I'm feeling pretty anxious.

strangeshapedpotato · 15/06/2021 13:38

Jesus - why is it that people are always second guessing professional instructions??

The tests are invalid after 30 mins! End of story!

One possible explanation would be that the tests are designed to be specific for covid but over a longer period of time they can react to other substances in your sample.

But it's irrelevant anyway - follow the instructions - STOP second guessing experts!

Yozhik · 04/07/2021 17:22

Did you do a pcr test? Same thing happened to me, twice! But I did a pcr test, just waiting for results.
I understand people here saying it's invalid after 30 minutes and it could be the same as an evaporation line on a pregnancy test. But still I have to wonder. Anyway, I guess a pcr test will tell me but it's excruciating to wait😫😂

Lalala73 · 08/08/2021 13:10

I would be interested in hearing about what your PCR results were for those showing a faint line after 30 mins. A few weeks ago this happened to my daughter . All 3 of her tests showed a faint line at around 40 mins . Got a PCR test and she was negative . Every lateral flow she has done since the same thing happens. Negative at 30 mins but then a faint line starts to develop afterwards .. this never used to happen and doesn’t happen to any other family member . It’s very annoying as I’ve lost complete confidence in the lateral flows now. I now always set the timer and always read her results at 30 mins. It’s not too much of an issue at the mo as she is under 11 and we are only testing to keep older relative safe but could become a problem as she gets older if lateral flows are required to get into places . Interested to know if this is happening to other people

CoComi · 10/08/2021 09:21

Hello,
Did you do the PCR test as it is same case here?

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