Hi,
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Primolut-N is sometimes prescribed to help in inducing a period and withdrawal bleeding after taking Primolut-N usually occurs after 2-3 days of taking the last pill dose. If pregnancy is suspected, you should consider visiting your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). If pregnancy gets ruled out, further evaluation would be done to look for underlying cause for your absent periods. Treatment as appropriate (based on examination findings and investigation results) would be started to help you get your periods and regulate them.
Take care.