getting once in a while plunges in his blood sugars; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient.  A 75-year-old male patient received BNT162b2 (BNT162B2), on 22Apr2022 as dose 4 (booster), single (Lot number: FK9893) at the age of 75 years for covid-19 immunisation; insulin detemir (LEVEMIR), on 28Mar2011 (Batch/Lot number: unknown) for diabetes mellitus. The patient's relevant medical history included: "Type 1 diabetes mellitus", start date: 1982 (ongoing); "SIBO" (ongoing); "High Blood Urea Nitrogen" (ongoing). Concomitant medication(s) included: NOVOLOG taken for diabetes mellitus; HUMALOG taken for diabetes mellitus. Vaccination history included: BNT162b2 (Dose 1; Lot: EN6208), administration date: 15Mar2021, when the patient was 74-year-old, for COVID-19 immunization; BNT162b2 (Dose 2; Lot: ER8737), administration date: 05Apr2021, when the patient was 74-year-old, for COVID-19 immunization, reaction(s): "irregular heart beat", "Diabetic Coma", "Blood glucose decreased", "car accident"; BNT162b2 (Dose 2; Lot: FG3527), administration date: 26Oct2021, when the patient was 74-year-old, for COVID-19 immunization, reaction(s): "Blood glucose decreased". The following information was reported: BLOOD GLUCOSE DECREASED (medically significant), outcome "unknown", described as "getting once in a while plunges in his blood sugars". The event "getting once in a while plunges in his blood sugars" required physician office visit. The patient underwent the following laboratory tests and procedures: Blood glucose fluctuation: 95; 117 down to 45; lose 60 points and go down to 40; blood sugar of 20; 95; blood sugar went below 70; gone down to 20; sugars were in the 90s; controlled sugars and he tries to keep, notes: controlled sugars and he tries to keep them in the 70s, but he can tolerate down to 40; sugar was 117 when he woke up and it went down, notes: blood sugar was 117 when he woke up and it went down to 40 within a few minutes; Electrocardiogram: 44 bpm; Glycosylated haemoglobin: 6 and below. The action taken for insulin detemir was unknown. Therapeutic measures were taken as a result of blood glucose decreased. Clinical course of the event: Patient reported a month after receiving the vaccine, his blood sugar would randomly drop low and plunge 30 minutes after administering Levemir and Lantus. Patient stated that he was 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. Patient stated since he has switched to Lantus, his sugar has plunged twice and he has been on Lantus since November. Patient reported that he has a well controlled A1C of 6 and below. Patient stated suddenly a month after taking it (the vaccine) this started happening. Patient stated it was too much of a coincidence and totally random. Patient reported that he always takes his medication at the same time and has a very routine schedule. Patient reported that he gets up in the morning checks his cgm receiver, matches the accucheck meter, and was stable before that reading. Patient stateed in the morning his sugar rises, but he was stable before that morning reading that can take 24 hours. Patient provided that he does not remember what medication he was on prior to 2011, but he took the medication every 12 hours. Patient reported this plunge "only when he wakes does this start to happen. Patient stated that he continuously monitors his cgm receiver and if it starts to go down remarkedly then he knows he has a problem. Patient stated that his sugar usually stays the same or goes up. Patient shared an incident in which he was on Levemir and provides that he did everything wrong. Patient stated he had been on Levemir, a 24 hour insulin made by the (Company name), since 28Mar2011 with no side effects and no problems. Patient 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. Patient stated with the Levemir it happened 5 times. Patient stated 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. Patient stated starting in May2021, about a month after his 2 vaccines, he started getting once in a while plunges in his blood sugars. Patient stated he would wake in morning and his sugar would be 95 and take his Levemir and within 30 minutes his blood sugars would start to plunge, he would lose 60 points and go down to 40. Patient stated he goes into a diabetic coma around a blood sugar of 20. Patient stated fortunately, he tolerates low blood sugars because he is well controlled. Patient stated this happened about 5 times between May2021 and the beginning of Oct2021.