When do pregnancy tests start working?
Pregnancy tests work by detecting human chorionic gonadotropin (HCG), a hormone that starts rising once a fertilised egg implants in the uterus. For most people, this happens 6 to 12 days after ovulation.
The earliest tests on the market claim to detect pregnancy up to “6 days before your missed period”. This is why some products are labelled as a ‘6 days early pregnancy test’ or an ‘early digital pregnancy test’. However, not everyone produces hCG at the same speed, and this affects how early a result can appear.
Why early testing can give negative results?
Even with a very sensitive self home pregnancy test, early results are not guaranteed. Some women have naturally lower baseline hCG levels, or their hormone rises more slowly in the first few days. This can lead to:
- False negatives: You may be pregnant, but the hormone level is still too low for the test to detect. Testing too soon means the strip or digital reader simply cannot pick up the hCG yet.
- Late implantation: If implantation happens on the later end of the normal range, your hCG won’t have had time to increase by the time you test.
- Testing at different times of day: Early in pregnancy, diluted urine can affect results. First-morning urine usually gives the most reliable early reading.
So, how early can you test?
If your cycle is regular, the earliest you should test is 6 days before your expected period, but a negative result at this stage is common. For the most accurate result, test from the day of your missed period, when hCG is far more likely to be detectable.
If your cycle is irregular, testing too early carries a higher risk of false negatives. Consider waiting until at least 14 days after ovulation, or repeat the test after 48 hours if unsure.
What to do after a negative early test?
If you tested early and got a negative result, wait two days and test again. hCG levels usually double every 48 to 72 hours in early pregnancy, so a second test often provides a clearer answer. If your period still doesn’t arrive and tests remain negative, it may be worth speaking with a healthcare professional, especially if your cycles are usually regular.
Find out more
For pharmacies supporting customers through early pregnancy testing, the Suresign range offers reliable options designed for clear, easy-to-interpret results. If you would like to explore Suresign pregnancy tests for your pharmacy or learn more about sensitivity levels across the range, please contact us for product details and support materials.

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