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Yes — Clearblue has a sensitivity of 10 mIU/ml and can detect pregnancy at 16 if HCG is above this threshold. Typical HCG at 16 is 250–750 mIU/ml. A faint line at 16 on Clearblue is a meaningful result.
A faint line on a Clearblue test at 16 DPO is a meaningful result. HCG at 16 DPO typically ranges from 250–750 mIU/ml — well above the 10 mIU/ml sensitivity of Clearblue in most cases.
If you are seeing a faint line at 16 DPO on Clearblue it is very likely a true positive, particularly if the line has blue colour and appeared within the 3 minute reading window. Retest in 48 hours with FMU and the line should be noticeably darker.
Clearblue uses blue dye. A true positive line on Clearblue at 16 DPO will be blue in colour — even if very faint. The key things to look for are:
A true positive Clearblue line is blue and has clear colour. Blue dye evap lines often appear grey or colourless. If the line has no blue colour it is most likely an evap.
Clearblue can occasionally produce evaporation lines. An evap line typically appears after the reading window and has no colour. If the line on your Clearblue test appeared within 10 minutes and has blue colour it is more likely to be a true positive.
Blue dye tests are more prone to evaporation lines than pink dye tests. Blue dye can spread unevenly and create a shadow or indent line that can be mistaken for a positive. Always read within the stated window.
Clearblue has a medium risk of indent lines.
An indent line is a colourless depression in the test strip where the test line would appear if positive. It is caused by the manufacturing process and is not a positive result. Key characteristics of an indent line on Clearblue:
- Has no blue colour — appears grey or colourless - Is visible on the dry test strip even before dipping - May become more visible on inverted or enhanced photos - Does not indicate pregnancy
At 16 DPO, typical HCG levels range from 250 to 750 mIU/ml. This is a wide range because HCG levels vary significantly between women and between pregnancies.
Clearblue has a detection threshold of 10 mIU/ml. This means:
The Mayo Clinic notes that HCG roughly doubles every 48 hours in early pregnancy. If you retest in 48 hours the line should be noticeably darker if HCG is rising as expected.
By 16 DPO HCG should be high enough to give a clear positive on all standard tests. A negative at this point is very unusual and warrants a repeat test and potentially a doctor visit.
48 hours is the recommended retest window after a faint result at 16 DPO. This is because HCG roughly doubles every 48 hours in early pregnancy — retesting after this interval gives the best chance of seeing a meaningful change in line darkness.
FMU is still recommended for the strongest result but any urine sample should give a clear positive by 16 DPO.
When retesting:
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Yes — a faint line at 16 DPO on Clearblue with blue colour that appeared within the reading window is likely a true positive. Retest in 48 hours to confirm progression.
Yes. Clearblue has a sensitivity of 10 mIU/ml. Typical HCG at 16 DPO ranges from 250–750 mIU/ml, so detection is possible in most pregnancies.
Evap lines on Clearblue typically appear after the reading window, have no blue colour, and appear grey or colourless. Clearblue has a medium risk of evaporation lines. A true positive Clearblue line is blue and has clear colour. Blue dye evap lines often appear grey or colourless. If the line has no blue colour it is most likely an evap.
An indent line on Clearblue is colourless — it has no blue colour and appears grey. Clearblue has a medium risk of indent lines. It is a depression in the test strip, not a positive result.
48 hours — FMU is still recommended for the strongest result but any urine sample should give a clear positive by 16 DPO.
Clearblue has a sensitivity of 10 mIU/ml — Other sensitive brands like FRER and Premom have similar or lower detection thresholds.
At 16 DPO, HCG typically ranges from 250–750 mIU/ml. If you are on the lower end of this range or implanted later, your HCG may barely exceed Clearblue's 10 mIU/ml threshold, producing a faint line. Retest in 48 hours — a rising HCG will produce a darker line.
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