Date: 202012
Local time of day: 1801-2400
Flight conditions: VMC
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Fatigue; Physiological - Other
Second reporter function: Captain; Pilot Flying
Anomaly: Flight Deck / Cabin / Aircraft Event Illness / Injury; No Specific Anomaly Occurred Unwanted Situation
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: While enroute and at cruise altitude of 39;000 feet; with between 1:00-1:15 hrs of flight time remaining of a 3:40 hour flight: my stomach began to feel queasy; I started sweating; and in a short time felt the urgent need for a bowel movement. I advised the Captain of my need to use the lavatory and contacted the flight attendants. I quickly got out of my seat due to the urgency in my stomach and went to the door. When I stood up rapidly; I felt a rush of nausea as well as feeling light-headed. When the flight attendants knocked; I opened the door. The next thing I know I am sitting on the galley floor with a nurse sitting next taking care of me; with a doctor assisting. The doctor and nurse monitored my vital signs; which initially both blood pressure and oxygen levels were low. I began to feel normal shortly after they had me drink some water and ½ cup of orange juice; utilize the onboard oxygen and began to administer 2 bags of IV fluid. Blood pressure and oxygen levels returned to normal.I told them that I had been fasting and had not eaten for nearly 2 days. I also said I could tell I was dehydrated due to the limited amount of urine output on our first lavatory break 1-1/2 hours into the flight. Both agreed that this was probably a cause for what happened and called it a vagal response; which can cause a person to faint.Upon landing; we were met by paramedics at the gate. They took my vital signs to include a blood glucose test. After completing their assessment; they said I was fine and there was no need to take me to the hospital. After being released from the paramedics; the entire crew of went to the crew van and the overnight hotel.Medical Assistance provided a Hospital for me to be seen; to ensure I was medically able to fly (as a passenger) back to ZZZ. I went to the Hospital and received: initial screening; EKG; and blood tests to include Electrolytes; Hemoglobin; Triage Cardiac screen 'CUANTITATIVO; (INCLUYE TROPONINA I; BNP; MIOGLOBINA; CKMB Y DIMEROS D)'The doctor stated that I was in excellent shape and saw no problems or issues with any of my test results. I was released with no further action nor medications required.


Second narrative: On Aircraft X ZZZ to ZZZ1 my FO (First Officer) said he needed a lav break; and I said go ahead; I have the aircraft. He got out of his seat and waited for the (FA) Flight Attendant to call so we could open the door. As the door opened and the FA came into the cockpit; he said boy your FO is very sweaty. Not more than 30 seconds later; the back end called and said the FO had passed out in the forward galley or first class. At that point; the FA stayed with me on the flight deck for the duration of the flight as he was talking on the phone and giving me vitals so I could send too Dispatch. We had an ER nurse taking care of FO and she set up an IV and he began to get better and told us he wants to continue to ZZZ1. FO was checked at the gate as well as going to ZZZ1 hospital and everything was good with no further action.


Synopsis: Air Carrier Pilots reported the First Officer became ill inflight and was unable to perform pilot duties.