Background I have had T1 for 39years (43 now) and have played outside all my adult life (mountaineering, trail running, biking, x-country & back country skiing plus a few tri's).
Reading your race the Insulin that you took at the beginning of the bike if it was (Humalog or Humulin) both start to react in ~20min's but do not reach there peak effectiveness until just under an <1hr.
So as you said for the first half of the bike you were just chasing the high. (Done that in one 1/2IM and I did not like it)
But others have commented adrenalane(epinephrine) at the start of the race can & does cause a high loading & converting of glucagon to glucose.
But since you become a bit low during the swim, in your case is the glucagon being released &/or converted more slowly?
So like everything else with diabetes it is trial & error.
But in my case I would give myself a small Bolus at the start of the swim and have an extra gel or two in the wetsuit in case.
Plus if you are using a pump and it is not on for the swim you are missing a small amount of insulin during the swim. i managed to have a look at my glucometer post 70.3
Full basal on board during the race, fully tapered.
1/2cup oats with protein shake for breakfast. Normal bolus to cover all about 2.5hrs before event.
No nutrition pre-swim, was 9mmols (162). Had a Gel halfway through swim as swimming drops me low in racing and training.
T1 = 5.5mmols, ate 2 gluogel jelly beans (15cals per bean, 4gms carbs mix of glucose/malto) - i wasnt expecting the reaction below!
7mins into ride = 10.1mmols (180) – injected a unit
+17mins = 14.4mmols (260) – from memory may have injected 2 units here
+25mins = 14mmols (252)
+32mins = 13.9mmol (250) – had a gel here with maybe 3 units? I know I injected again
+38mins = 16.4mmols (295)
+48mins = 12.3mmols (221)
+58mins = 12.7mmols (228) – may have had more nutrition here with more insulin
+1hr05 = 13.4mmols (241)
+1hr15 = 14.4mmols (260) – injected more
+1hr25 = 7.9mmols (142) and the rest of the ride AND run between 4-8mmols.
At a guess I took about 7 units of insulin during my ride, unfortunatley i cant remember how much but it was a shit tonne.
It took me 1hr25mins to bring blood sugar down on the bike. No wonder I had a good first lap, I was perhaps cycling on stored glycogen in muscle? but ran out of gas and cramped badly just when my sugars were good again in the latter part of the ride and run.
Resurrecting this thread:
70.3 strategies on mdi and tapered
- what works for you? How do u settle those highs? Inject before the swim ? In t1? Reduce ur basal the night before?
Tired of the bike portion sending me high that it ruins the rest of my races. Injecting 7 units on the first 40 kms of a bike leg is racing blood sugar not the race and not my idea of fun