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Yes — FRER has a sensitivity of 6.3 mIU/ml and can detect pregnancy at 18 if HCG is above this threshold. Typical HCG at 18 is 600–2000 mIU/ml. A faint line at 18 on FRER is a meaningful result.
A faint line on a FRER test at 18 DPO is a meaningful result. HCG at 18 DPO typically ranges from 600–2000 mIU/ml — well above the 6.3 mIU/ml sensitivity of FRER in most cases.
If you are seeing a faint line at 18 DPO on FRER it is very likely a true positive, particularly if the line has pink colour and appeared within the 3 minute reading window. Retest in 48 hours with FMU and the line should be noticeably darker.
FRER uses pink dye. A true positive line on FRER at 18 DPO will be pink in colour — even if very faint. The key things to look for are:
A true positive FRER line is pink and has colour — even a very faint FRER positive should have a distinctly pink hue rather than appearing grey or colourless.
FRER has a relatively low risk of evaporation lines compared to other brands. However an evap is still possible if the test is read after the 10 minute window. Always read within the stated time.
Occasional dye runs can cause a faint pink wash that is not a true positive. Hook effect possible at very high HCG levels. Some users report indent lines but less common than with strips.
FRER has a low 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 FRER:
- Has no pink 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 18 DPO, typical HCG levels range from 600 to 2000 mIU/ml. This is a wide range because HCG levels vary significantly between women and between pregnancies.
FRER has a detection threshold of 6.3 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.
18 DPO represents approximately 4 weeks pregnant. HCG should be well established and giving strong positives across all test types.
48 hours is the recommended retest window after a faint result at 18 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.
Any urine sample gives a reliable result by 18 DPO.
When retesting:
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ClearLine uses AI to analyse your FRER test photo and detect even the faintest lines. Enhance your image with brightness, contrast and red light filters to see lines more clearly. Save and compare your tests side by side to track line progression.
Also see:
Also see:
Related guides:
Yes — a faint line at 18 DPO on FRER with pink colour that appeared within the reading window is likely a true positive. Retest in 48 hours to confirm progression.
Yes. FRER has a sensitivity of 6.3 mIU/ml. Typical HCG at 18 DPO ranges from 600–2000 mIU/ml, so detection is possible in most pregnancies.
Evap lines on FRER typically appear after the reading window, have no pink colour, and appear grey or colourless. FRER has a low risk of evaporation lines. A true positive FRER line is pink and has colour — even a very faint FRER positive should have a distinctly pink hue rather than appearing grey or colourless.
An indent line on FRER is colourless — it has no pink colour and appears grey. FRER has a low risk of indent lines. It is a depression in the test strip, not a positive result.
48 hours — Any urine sample gives a reliable result by 18 DPO.
FRER has a sensitivity of 6.3 mIU/ml — Other sensitive brands like Clearblue and Premom have similar or lower detection thresholds.
At 18 DPO, HCG typically ranges from 600–2000 mIU/ml. If you are on the lower end of this range or implanted later, your HCG may barely exceed FRER's 6.3 mIU/ml threshold, producing a faint line. Retest in 48 hours — a rising HCG will produce a darker line.
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