What could change menstrual flow from heavy to light, mid-period?

I think it's a concern when you are used to your period being a particular way and while you might think light is great...(it is! ) If it's not what you usually experience then it's quite unsettling. I usually have a heavy flow, like change the pad every couple hours, monster put me in tears and make me almost pass out cramps. About 3 months ago it changed. Suddenly, it's so light one pad a day would be sufficient for the flow and it only lasts about 4 days and there are hardly any cramps if at all! I am not pregnant, haven't gained or lost weight, but it is certainly not normal. The only new thing is exactly 3 months ago I started a new job. But I didn't start my night shift until 2 months ago. It's very unsettling to me. As soon as my health insurance kicks in I am definately calling a doctor.

I am concerned myself. For the last couple of months my period has changed dramastically. it's gone from heavy flow to lite sometimes not even spotting the pad at first and then slowly changing to a normal flow but nothing like it used to. i have gain some weight and was told that might be the reason.

i have the same problem with you girl i had a heavy flow, had my period in the 4th or 3rd grade and it turned light at my age, dont know if its the same situation but yeah

What are you specifically concerned about, as I would not consider this a "dramatic" change??

Please know that your period will change throughout your life, depending on if you have had a recent illness, medications (vaccines may/may not effect your cycle the following day..I doubt they would), excess stress...or any number of environmental influences. The changes you experience can include flow that is heavier or lighter; longer or shorter in duration; different color (red, pink, brown), thicker or thinner, etc.

Your menstrual cycles will change many times throughout your life; sometimes it will be predictable and other times there will seemingly be no "rhyme or reason" to the change. Your hormones fluctuate on an on-going basis during your cycle, as your body reacts to its environment. This is normal, and healthy, as our bodies are not built to run like clockwork, even if previously you could count on your period to be precise.

Your menstrual period may be the exact same for months or years, then change for no apparent reason. As long as it is still within the normal ranges, this is fine. Normal ranges for a period means that your cycle is about 21-35 days long, and you don't bleed for more than about 7 days. Some women experience PMS symptoms, others do not. Some women have late periods or even miss a period one month (and is not due to a pregnancy), and this can be normal, too. What's not normal is abnormal heavy bleeding (soaking more than 1-2 pads/tampons every hour), extreme pain, period lasting more than 7 days. You can read more at: How to know if your period is normal.