Hi there,
There is a big long paragraph in the booklet that comes with the monitor in relation to the Limitations on Use for it. If you bear with me, I will write here what it says word for word:
Apologies for the length of post by the way. But there is information here that does not feature on the Clearblue website and the only way of reading it would be to buy a monitor and open the packaging. I hope it helps some of you.
"The Clearblue Fertility Monitor is suitable for women whose natural cycle normally lasts between 21 and 42 days. The majority of women will need 10 Test Sticks in each cycle. However, women with irregular or long cycles may have to use 20 Test Sticks each cycle in order to detect their most fertile time.
Certain medical conditions and medications can adversely affect the performance of the Monitor. Women who have menopausal symptoms, polycycstic ovarian syndrome, impaired liver or kidney function, are pregnant or have recently been pregnant (even if not carried to full term), may get misleading results. Similarly misleading results may be obtained by women using antibiotics containing tetracyclines, hormonal treatments (eg hormonal contraception, hormone replacement therapy), fertility treatments containing human Chorionic Gonadotrophin (hCG) or Luteinising Hormone (LH), or any treatment that might affect their cycle. Clomiphene citrate may elevate estrogen levels and this may result in High Fertility being declared early in the cycle and more High Days being displayed, and in some cases the Monitor may not show Peak Fertility even when ovulation occurs. We therefore recommend that women taking clomiphene citrate consult their doctor for advice before using the Clearblue Fertility Monitor. Always read the manufacturers instructions for any medication that you are taking before conducting a test.
Women who have recently been breastfeeding, using hormonal treatments (eg hormonal contraception, including emergency contraception, fertility treatments, hormone replacement therapy), or any other treatment that might affect their cycle, may wish to wait until they have at least two natural menstrual cycles in a row (each lasting 21-42 days), before using the Clearblue Fertility Monitor.
Women who have recently been pregnant (even if not carried to full term) may still have hCG in their bodies. HCG can adversely affect the performance of the Monitor. Therefore they are advised to wait until they have had at least two natural menstrual cycles in a row (each lasting 21-42 days), before using the Clearblue Fertility Monitor.
Please speak to your doctor if you need further advice."