T1D game plan for my first full distance Ironman

Giovanni Tertulli

7 min read

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Oct 11, 2026

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One week out from Ironman Portugal — Cascais.

Id like to sit here and tell you about all the emotions, feelings and thoughts coming and going through my head. But I will leave that kind of article for *after * the race. As I type these words, I feel a need to be practical and lay down the strategy to manage my blood sugars during what I expect to be a 12–14 hours race.

Next Saturday, I want to walk towards the starting line with elite clarity about what to do, and what not to do.

I am sure there will be nuances and last minute adjustments I will need to make, and I have no intention to do there and just react — I want to have a framework to operate within and be proactive.

So, after months of training and observing my blood sugars fluctuating, here’s what I am planning to do.

PRE RACE — Carb lading

Of course, I’ll be putting fuel in the tank in advance.

Three days out, I am going to gradually reduce fiber and swap whole grains for refined grains (brown pasta > white pasta). For sure, I am not going to eat any legumes, so proteins are going to come from soy products (soy milk, tofu, etc) for the most part.

To be more specific, the targets are

• 6–8g carbs per KG of bodyweight three and two days out
• 8–10g carbs per KG of bodyweight one day out (with very small fiber)

But since I don’t want to end up in a massive calorie surplus, I am going to adjust based on my maintenance calories — probably, by lowering fats and proteins a bit.

Blood sugar wise, carb loading is tricky because you’re moving less, eating more carbs, and also more processed carbs (which carry a higher likelihood of spikes).

The strategy is straightforward:

• drink lots of water (so insulin travels faster)
• increase the I:C ratios (I will start with a 10% increase and adjust as I need)
• extend my pre-bolus time (if I used to wait 10 minutes to start eating, I am going to wait 15, 20, 30)
• Eat slowly
• Reserve any movement (such as preparing the bike for transition, visiting the expos, etc) for AFTER the meals, so I tame the spikes
• Stop eating relatively early, so I catch and treat any upward trend before hitting the bed

Based on my experience in previous races, these tweaks work pretty well.

RACE DAY — Morning (until swim start)

This is where I tend to make the most mistakes.

Usually, I wake up early (~3h before the race), deliver a normal dose of insulin immediately and wait until I feel it’s the right moment to eat. That has always worked well, except that when I get closer to the starting line I start being worried about having low blood sugars in the open water.

The mix of adrenaline, anxiety and worry leads me to eat more (rice cakes or a gel), and produce a spike I carry for the first few hours of the race.

I am determined to avoid this, here’s how:

• the “ghost carbs” trick. Say I dose for 50g carbs, I will only eat 30. Those 20 I leave out of my meal are the “ghost carbs”, and are usually compensated by an adrenaline spike (which is now covered by insulin). If I have a lower trend I can always eat later if needed.
• mixing carbs with proteins. This is less ideal because proteins aren’t great for the stomach on a long day of endurance sports, but a tiny amount solves many problems. I’ve tried this in training: instead of a slice of bread, I sip some unsweetened soy milk one hour before the start. It doesn’t produce an immediate rise in blood sugars, but it only kicks in later on (when I am already moving, and thus counteracting the spike).
• Breathing deeply. If there’s one thing that has the power to prevent any anxiety-induced mistake and keep blood sugars in range, it’s staying calm. Breathing deeply through the nose and making longer exhales will help both tame the adrenaline, and keep myself lucid.

That’s the approach.

In practice:

• wake up at 4:30
• dose for 50g carbs and wait 20–30’ (normal I:C Ratio)
• eat only 30g carbs, slowly
• disconnect my pump and leave it in the bike transition area
• get to the starting line in range by 6:30, breathing deeply, with only a minimal amount of residual insulin in board
• ask someone from the organization to keep my blood sugar meter (so I can get a few final readings before entering the water)

And of course, carrying 4 gels in my wetsuit (two in the forearms and two in the ankles) for any emergency.

RACE DAY — Bike leg

After I get out of the water, I will immediately reach the bike and connect the pump.

Depending on the first couple blood sugar readings, I will decide whether to correct with insulin:

• if between 200 and 300, I will add a correction (during workouts, I 2.5X my correction factor. So what used to be 30 is now 85). Then I wait until I am below 200 to start eating my gels
• if below 200, I start eating immediately but slowly — one sip every 10’ to avoid spikes
• if below 150, I just take one full gel immediately (40g carbs) and start pedaling

Any other insulin dose will be microscopic.

During training rides, even 0.2U could drop me from 200 to 120 in less than half an hour, and I can’t afford such wide swings during an Ironman — especially because any insulin I will add, is going to kick at some point. Usually, that’s during the run — and good luck treating lows for 42km straight.

In my 190km training ride, I only dosed a couple units at the start and got away with 80g carbs per hour for 8 hours straight.

That’s what I intend to replicate.

The key thing will be staying lucid and avoid reactive or impulsive actions — such as rage bolusing or stacking doses because blood sugars are too high. That’s a guaranteed low and potentially a DNF.

In the event my blood sugars are too high during the bike, I will focus on drinking water (with the appropriate amount of sodium per liter I need), and then eat micro doses of carbs (5–10g) based on my CGM. Even if my readings are above 200, if the arrow points downwards I know that’s my moment to start eating.

That works better because I am “accompanying” my blood sugars down to range instead of letting them crush.

RACE DAY — Run

Ideally, I have fuelled the bike leg as per plan and get to the run with a tank full of gas and hydrated (water and sodium).

If for whatever reason I end up eating less carbs, I know I will have to adjust my pace to get to the finish line. Luckily, I know myself very well and I know I can do that — I’ve ran 100km eating barely a couple gels and a small pot of pasta, and an half Ironman eating less than half the fuel I meant to eat.

The important thing will be managing the insulin well during the bike (that includes stopping insulin for prolonged periods of time), so I don’t start the marathon with insulin on board that sends me to hypoglycemia.

There’s a risk that the stomach shuts down at some point, and people can’t eat or drink when that happens.

We don’t want to be in hypoglycemia in that case, don’t we?

Then, I will do as always during Ironman: stop at every aid station, sip some Coca Cola, grab one extra gel and keep running. If I need to visit the toilet, I will visit the toilet. If I need to walk for a bit, I will walk.

Anything that can keep my blood sugars stable and in range while I approach the finish line, I will do.

As far as insulin goes, if everything goes well I shouldn’t need any of it — my insulin sensitivity will be so high that any amount of basal insulin would be too much, and any rapid insulin would shoot me down. That is UNLESS my blood sugars are running higher than 200, in which case I will adjust with micro 0.05U every 20–30’ and with EXTREME caution because — once again — even the smallest amount of insulin can be too much at this point.

Then, if my blood sugars are stable around 130–150, I am going to deliver 1/2 of my usual dinner dose 10–15’ before crossing the finish line.

Why? Because:

• the moment I stop moving, digestion is going to resume and all the carbs I’ve been eating on course will kick in (so I need to get ahead of the spike)
• AND because Ironman offers a rich buffet in the athletes tent, and I want to be able to eat some real food as soon as I finish.

Once again, if I feel not OK during the run, I am not going to dose any amount. I want to avoid having insulin on board and not being able to eat any food — that’s a guaranteed visit to the hospital.

You’ll know how it all played out in one of the next articles!