Lucy Flynn, BABYGO® team
It's five days before your period is due, the box says you can test now, and you've read the leaflet three times. What you want to know is whether "now" is actually worth it.
Here's what Clearblue's early test claims, what the NHS says about when a pregnancy test works, and why a negative this week doesn't settle anything.
Quick answer: Clearblue says its Early Detection test can be used up to six days before your missed period, which is five days before the day you expect it. The NHS says most tests work from the first day of a missed period, that a positive is almost certainly right, and that an early negative is less reliable. If it's negative, test again in a few days.
What the NHS says, in numbers:
- Every pregnancy test looks for the hormone hCG, which starts to be produced around 6 days after fertilisation.
- You can do most tests from the first day of a missed period. Some very sensitive tests can be used before you miss a period.
- Not sure when your period is due? Test at least 21 days after you last had unprotected sex.
- A positive result is almost certainly correct. A negative is less reliable.
- Any time of day is fine for the sample. It doesn't have to be the morning.
How early does Clearblue Early Detection work?
Clearblue's Early Detection test is the one sold for testing before your period is due. The claim on the box is that it can be used up to six days before your missed period, which Clearblue counts as five days before the day you expect your period to start. The "missed period" day is the day after the one you were expecting it.
Two things to hold onto about that claim. First, "can be used" isn't "will find it". Clearblue prints a detection rate for each of those early days on the pack, and it climbs day by day, from well short of certain at six days out to over 99% from the day your period is due.
Second, that over 99% figure is for the day your period is due and after, which is the same point the NHS says most tests work from.
So the honest way to read the pack is this. You can test six days early, and if it's positive, that's real. If it's negative, you've learnt nothing yet.
When to test with a Clearblue
The NHS page on doing a pregnancy test is where I'd send anyone, whatever brand they've bought. Its rules are short, so here they are next to Clearblue's claim.
| When you test | What to expect |
|---|---|
| Six days before your missed period | Clearblue's earliest claim, for its Early Detection test. A positive counts. A negative means very little |
| The days in between | Detection rates rise day by day, according to the pack. Still early |
| The day your period is due | Clearblue claims over 99% accuracy from here. The NHS says you can do most tests from the first day of a missed period |
| A few days later, still negative, no period | The NHS says wait a few days and try again |
| Second negative, still no period | The NHS says speak to your GP |
| Not sure when your period is due | The NHS says test at least 21 days after you last had unprotected sex |
Time of day matters less than people think. The NHS says you can test on urine collected at any time of day, and it doesn't have to be the morning.
Clearblue's leaflet adds one thing for early testing: if you're testing before your period is due, use the first wee of the day, because that's when the hCG in your urine is most concentrated. Once your period is late, any time works.
If it's two lines, the next question is when. Our due date calculator works it out from your last period, and covers IVF and IUI dates too.
Just got a positive? Tell us your due date and we'll send what to expect, what to do and what to sort each week, starting now. 10% off when you're ready.
Why an early negative doesn't mean you're not pregnant
Home tests and blood tests look for the same hormone, human chorionic gonadotrophin, hCG for short. The NHS says it starts to be produced around 6 days after fertilisation, and the level rises quickly over the first weeks. A test can only find it once there's enough in your urine to react to, so the earlier you test, the better the odds there isn't enough yet.
That's the whole reason the NHS calls a negative less reliable than a positive. A negative six days early can mean not pregnant, or pregnant with not enough hCG yet, or a test done wrong. A positive is almost certainly right, the NHS says, because the hormone has to come from somewhere; the rare exceptions are in our piece on false positive pregnancy tests.
So if it's negative and your period doesn't turn up, wait a few days and test again, and if the second one is negative too, speak to your GP. For the test itself, the dip, the wait and how to read the window, there's a separate short piece on how to use a Clearblue pregnancy test.
Questions we get asked
Can I use a Clearblue 7 days before my period?
Clearblue's earliest claim is six days before your missed period, which is five days before the day you expect it, and that's for its Early Detection test. Seven days out is outside what that box claims, and a negative that early tells you nothing. Wait a day or two.
How early can Clearblue Digital detect pregnancy?
It depends which digital test you've got. Clearblue sells more than one, and the number of days before your period each can be used is printed on the front of the box. Whatever it says, the NHS rule still applies: a negative before your period is due isn't reliable, and a positive almost certainly is.
Should I use first morning urine for an early test?
If you're testing before your period is due, yes. Clearblue's leaflet says the first wee of the day, because the hCG in it is most concentrated then. Once your period is late it doesn't matter, and the NHS says a sample from any time of day is fine.
What does "days before your missed period" mean on the box?
Clearblue counts your missed period day as the day after the one you expected your period. So six days before your missed period is five days before the day it's due. If your period is due on the 20th, the missed period day is the 21st, and six days before that is the 15th.
How soon after sex can a pregnancy test detect pregnancy?
The hormone the test looks for starts to be produced around 6 days after fertilisation, the NHS says, and most tests work from the first day of a missed period. If you don't know when your period is due, the NHS advice is to test at least 21 days after you last had unprotected sex.
The pregnancy collection is there for when the testing stage is over and the next one starts.
This is general guidance from the BABYGO® team, not medical advice. Your midwife or GP knows your pregnancy; ask them if anything here doesn't fit your situation.
