Adrenaline and competition nerves
Why nerves before a match can raise your glucose before you have moved a muscle, and what helps.
Nerves before a match, a race or a big game can push your glucose up, even before you have moved a muscle. That is adrenaline, the stress hormone your body releases when you are wound up, and it tells your liver to dump extra glucose into your blood. Then, once you actually start playing, activity often pulls glucose back down, sometimes fast.
- Adrenaline (the fight-or-flight hormone) can raise your glucose before an event, so a high reading beforehand may be nerves, not food.
- Once you start moving, that same adrenaline effect can fade while exercise lowers your glucose, so you can swing from high to low in one session.
- A pre-event high often does not need treating the same way a post-meal high does, because it can drop on its own once you are playing.
- Watch for delayed lows: glucose can keep falling for hours after the event, including overnight.
Why nerves push your glucose up
Adrenaline is what your body releases when it thinks something big is about to happen. A race start, walking out for a match, an exam, a job interview: your body treats them all as a threat it needs energy for. One of the things adrenaline does is tell your liver to release stored glucose, so there is fuel ready for muscles to use.
For someone without type 1, insulin rises to match that release and the level barely moves. Your body cannot do that on its own, so the extra glucose has nowhere to go and your reading climbs. This is why you can be sitting still, having eaten and dosed normally, and still watch your glucose drift up before you have done anything.
The swing from high to low
The tricky part is what happens next. Adrenaline is short-lived. Once the event starts and you settle into playing, the surge fades. At the same time, most activity burns glucose, so the level that was high can turn and drop, sometimes quickly.
If you had treated the pre-event high with a correction dose, you would then be lowering an already-falling glucose, and a hypo becomes much more likely (a hypo is a low, below 4 mmol/L, where you feel shaky, sweaty or confused and need fast sugar). That combination, correcting a nervous high just before exercise, is one of the more common ways people end up low mid-game.
What changes how this plays out
Not everyone spikes with nerves, and not to the same degree. A calm, familiar training session may barely move you, while a final or a first competition sends you up. Short, explosive efforts (a sprint, a lift, a penalty shootout) can add their own adrenaline-driven rise, while longer steady activity (a distance run, a long walk) tends to pull glucose down. Insulin already in your system from a recent meal matters too, because it keeps working through all of this.
How this can look
Examples, not instructions or doses.
You have eaten and dosed as usual, done nothing physical, and your glucose reads 12 mmol/L half an hour before kick-off when you would normally be around 7. Nerves are a likely explanation, and it may come down once you are moving.
You start the match high on adrenaline, then twenty minutes in you feel shaky and your glucose is 4.5 and falling. The surge has worn off and the running is using glucose, so you are heading for a hypo.
The competition finished hours ago and you are fine, but your glucose keeps dipping through the evening and into the night. Muscles are still refilling their glucose stores, so a delayed low is possible long after you stopped.