Please advice - severe hypotension linked with exercise and monthly cycle?

This is the second occurrence I've have this year of these episodes and theres 2 common factors each time. I'm on a normal training run and; its just before I'm due to start my monthly period I should add I run and train regularly with no incident and consider myself physically fit First occurrence -3... show more This is the second occurrence I've have this year of these episodes and theres 2 common factors each time.
I'm on a normal training run and;
its just before I'm due to start my monthly period
I should add I run and train regularly with no incident and consider myself physically fit
First occurrence -3 months ago had a 3 mile run planned, was 1 mile in and started to feel unwell so sat down on a bench and decided it'd walk the mile home, started feeling even worse had to sit down every couple of metres got to a shop and contemplated asking for an ambulance I felt that bad, my hearing was going and I knew I was about to faint, didn't have my phone on me to call anyone. Sat down had a chocolate bar and water (was thinking it could be blood sugar) and some ibrofen for lower stomach cramp like pain. Recovered in 15 minutes and walked home.
Second occurrence - today, had a 2 mile run planned, got 0.7 miles in and decided to turn round as was feeling unwell, ran back, had about 300 metres left and had to sit down. Felt like i might thrown up. Home this time and curious if my blood pressure was low, my mums got a home machine for high blood pressure, I (barely) took a reading stood up. It was 78/26, I lay back down and it took about 10 minutes to recover, both times i have not an unbearable, but a definite lower abdo cramps.
What is physiology going on? Would a trip to my GP warrant investigation or is this just something I should manage (e.g not running just before i'm due on)
1 answer 1