Bloodwork at 34 weeks?

I saw my doctor yesterday. He gave me meds for my gestational diabetes and something for this mirgaine that never goes away ever. My blood pressure was 124/81 and nurse said that was good though online it says high is 130/90 so its like right there.

They took urine and he suggested a bladder infection as well and asked if i had burning when i peed and i explained i didn't and then he said he'd send it to a better lab just in case since he wasn't sure so he didnt prescribe anything. I mostly think he suggested it because my pee was dark but i think that was due to me not drinking enough water the past week because of feeling sick because of my migraines.

I wake up to a call this morning from a nurse explaining my doctor ordered bloodwork to be done and for me to go in sometime this week to get it done at the lab but she didnt mention why. Why would i not be told this yesterday and why would they need bloodwork so randomly. I know with my first they tested me for anemia at the end of my pregnancy but that was at like 36 weeks and i got it done the same day. Ill be 35 weeks tomorrow and wasnt told about needing any bloodwork at my appointment where i could've gotten it done the same day.