irregular heart beat; Blood Sugar in 20s; Diabetic Coma; he didn't go to the ER after his car accident on 14Aug2021; in May2021 he started having the following side effect of totally random plunges in his blood sugars after taking his Levemir; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient. Other Case identifier(s): 20220602793.  A 75-year-old male patient received BNT162b2 (BNT162B2), on 05Apr2021 as dose 2, single (Lot number: ER8737) at the age of 74 years, in left arm for covid-19 immunisation; insulin detemir (LEVEMIR), since 28Mar2011 (Batch/Lot number: unknown). The patient's relevant medical history included: "Type 1 diabetes mellitus", start date: 1982 (ongoing); "High Blood Urea Nitrogen" (ongoing); "SIBO" (ongoing). Concomitant medication(s) included: HUMALOG taken for diabetes mellitus; NOVOLOG taken for diabetes mellitus. Vaccination history included: BNT162b2 (First Dose: 15Mar2021 Lot: EN6208), administration date: 15Mar2021, when the patient was 74-year-old, for COVID-19 immunization. The following information was reported: BLOOD GLUCOSE DECREASED (non-serious) with onset May2021, outcome "recovered" (Nov2021), described as "in May2021 he started having the following side effect of totally random plunges in his blood sugars after taking his Levemir"; ROAD TRAFFIC ACCIDENT (non-serious) with onset 14Aug2021, outcome "recovered" (14Aug2021), described as "he didn't go to the ER after his car accident on 14Aug2021"; DIABETIC COMA (medically significant) with onset Oct2021, outcome "recovered" (Oct2021), described as "Blood Sugar in 20s; Diabetic Coma"; HEART RATE IRREGULAR (non-serious), outcome "recovered", described as "irregular heart beat". The events "blood sugar in 20s; diabetic coma", "in may2021 he started having the following side effect of totally random plunges in his blood sugars after taking his levemir", "he didn't go to the er after his car accident on 14aug2021" and "irregular heart beat" required physician office visit. The patient underwent the following laboratory tests and procedures: Blood glucose abnormal: (May2021) random plunges; Electrocardiogram: (unspecified date) 44 bpm; Glycosylated haemoglobin: (unspecified date) A1C of 6 and below. The action taken for insulin detemir was unknown. Therapeutic measures were taken as a result of diabetic coma.  Clinical course: SIBO, Small Intestinal Bacteria Overload faulty bacteria in his intestines so he takes Biaxin every 6 months to kill the bacteria in his intestine. Also Safactin. Patient received two doses of the Pfizer Covid-19 vaccine. He reports a month after receiving the vaccine, his blood sugar would randomly drop low and plunge 30 minutes after administering Levemir and Lantus. He is a stable Type 1 Diabetic who has been taking Levemir since 28Mar2011 and has taken Levemir for years and had no problem, however his sugars were plunging monthly, so his physician switched him to taking Lantus 15 units. Since he has switched to Lantus, his sugar has plunged twice and he has been on Lantus since November. He has a "well controlled A1C of 6 and below. This plunge only when he wakes does this start to happen. He continuously monitors his cgm receiver and if it starts to go down remarkedly then he knows he has a problem. He left his house when his sugar was at 95, then got in the car to go to the beach to sail. He got off of the freeway and had an accident due to his sugar plunging to 20 within a matter of a few minutes. His sugar plunged as soon as he took Lantus both times, but normally his reaction is delayed several hours. Lantus has been less problematic than Levemir, as his plunges were occurring more frequently with Levemir. His sugars plunged this last week from 117 down to 45. In emergency situations he use maple syrup. He has SIBO (small intestinal bacterial overload) in which he has to take Safactin which selectively kills bacteria in his intestines, which could wack his sugars. He has a PhD and he is a Air Quality Meteorology Research Scientist. When he wakes up in the morning his continuous meter, the Dexcom G6, gives him readings every 5 min of his interstitial blood sugars and he checks them against his finger stick glucose meter. Reporter stated 1 month after taking the Covid 19 Vaccine 2 shot vaccine series, in May2021 he started having the following side effect of totally random plunges in his blood sugars after taking his Levemir. Reporter stated one time it happened when he was driving a car and that was bad news and he had an accident. Reporter stated his sugar when he left his house was 95. it was his mistake, he had his continuous meter in his hip pocket, and he had the radio on and the windows down so he didn't hear it alarming when his blood sugar went below 70 and started alerting. he was going to meet his buddies at the marina and 5 minutes away, he ran into some parked cars at a signal because his sugars had gone down to 20 and he goes into a diabetic coma around a blood sugar of 20 and all of  that has been taken care of now, he just didn't stop in time because he was in a diabetic coma and barely functioning. In October it happened another time, he woke up and his sugars were in the 90s and he took his 24 hour insulin and he had been stable over night as determined by his every 5 minute continuous monitor and at about 7:10a.m. he was standing in line at buffet and the next thing he knows the paramedics are giving him sugar through an IV because his blood sugar was just below 20. Caller states he is used to well controlled sugars and he tries to keep them in the 70s, but he can tolerate down to 40. They gave him the IV sugar feed and then he was fine. Reporter stated he thinks this is from the vaccine because it has happened with 2 different types of insulin and he was very stable before the vaccines. he wants to know if anyone on has reported anything like this, his Doctor says this has got to be pretty rare because he is a research endocrinologist and he sees a lot of diabetic patients and he said he hasn't seen it in anyone else and he hasn't had it reported by anyone and he works with other diabetic doctors there in the complex so it has got to be pretty rare. Reporter stated he thinks it is the vaccine that has done this, but he is not going to stop taking the vaccines. He has never had this problem with Humalog or Novalog, which he uses those too. Reporter stated even a person like him that is well controlled and has no diabetic side effects like neuropathy or eye problems, doctors think their body is still compromised with diabetes, its never been proven, but that is the general feeling by doctors. Patient did not received additional vaccines on same date of the pfizer suspect. No prior vaccinations (within 4 weeks). The vaccination facility type was university and pharmacy/drug store. The patient received Boosters: 26Oct2021 Lot: FG3527, Booster 22Apr2022 Lot: FK9893. The adverse event (AE) details: provide the time of onset of AE(s) was 1 month after second dose. . Reporter stated he didn't go to the ER after his car accident on 14Aug2021 because they would take his license away for 6 years. Reporter stated he recovered very quickly and they said do you want to go to the ER and he said no, and they were very cooperative and nice. No hospitalizations.  Physician Office visit was yes. Tested positive for Covid 19 after receiving 3 doses of the Pfizer Covid 19 Vaccines.  Follow-up attempts are completed. No further information is expected.