My MdS: As told by my glucose levels

Not long ago I ran 140 miles over six days in the Sahara Desert with a Dexcom G6 continuous glucose monitor and an Omnipod insulin pump taped to my belly, while wearing SHORT shorts that looked more like a netball skirt. I don’t like to talk about it all that much, but you can read about it here, here and here if you fancy it.

The Marathon des Sables 2019 is one of the greatest things I’ve ever done. Not just because of the amazing places I saw, the friends I made and the boundaries I broke; it also taught me valuable lessons about myself, type 1 diabetes and how I can stop it limiting what I do in life.

Dexcom lessons

For anyone who knows what well managed glucose levels should look like, what follows may be akin to a horror story. My levels were all over the place during the MdS. Perhaps that’s not surprising, given all the exertion, heat, cold and adrenaline. I’ve also since discovered that medication I was on then can make glucose control trickier (more on that another day).

“This is the story of my MdS, as told by my glucose levels, and the lessons I learned along the way…”

Sky high levels did at times make me feel ill. Hypos in 45°C heat, miles from civilisation, are scary. But, in spite of the rollercoaster my levels were on, I still look back on the MdS and wish I was there again. The challenge of trying (and mostly failing) to keep my glucose levels in range while running up to 50 miles a day maybe even added to the experience.

I have so much to thank Dexcom, which gave me a G6 for the MdS, to thank for. The G6 meant I went into the desert without having to constantly prick my fingers to monitor my levels. Instead, the G6 transmitted readings from a sensor embedded in my abdomen to my watch via my phone and, crucially, showed me the direction my level was heading in.

It also taught me some valuable lessons about running stupidly long distances in deserts with type 1 diabetes. I hope I can put them to good use in another race one day soon. So, here is the story of my MdS, as told by my glucose levels, and the lessons I learned along the way…

Diabetes wants me to stay home (I want to go running)

Type 1 diabetes likes routine. It hates surprises. It would much rather I just stayed at home and put my feet up. See, unfamiliar surroundings tend to come with unfamiliar food, making calculating insulin dosage for what I’m eating very difficult. Secondly, fear and excitement can cause stress hormones such as adrenaline and cortisol to be released. These send messages to the liver, prompting it to release glucose into the blood, causing sugar levels to spike.

The below graphs show my levels in the 48 hours before the MdS, which were mostly spent travelling and preparing in the desert. This involved kit and medical checks and a lot of waiting around and eating. The organisers put on huge buffets and I filled up, knowing I’d have to be self sufficient from 7 April. The spikes show when I ate. They also show that my insulin dose was way off; my levels were far higher than my target range of 3.9 to 10mmol for much of the time.

glucose levels 4/5 AprilHypoglycaemia (low blood sugar) can cause confusion, convulsions and unconsciousness and I feared a serious hypo would stop my race before it had even begun, so was happy to run on the high side to cut the risk of a hypo. But the difficulties I had calculating insulin dosage and those stress hormones sloshing around my system made control difficult. My glucose level soared. The higher my level, the thirstier and more lethargic I felt.

I seemed to be less sensitive to my insulin (at least when it wasn’t so hot; see below), so needed to take more to bring my levels down. I over-corrected, leading to hypos before my evening meals. I was able to treat these myself and, thankfully, they went unnoticed by anyone else. I sat down for the ‘final supper’ on 6 April with tingling lips and shaky hands from the hypo I’d just had and piled my plate high. The meal was a kind of nervous celebration with lots of laughter and carbohydrates.

We were all buzzing as we walked back to our tents. I was so excited. The desert was everything I’d expected: hot, huge, beautiful and scary. It made me feel tiny yet so alive. But I felt like shit. My blood was sky high. My mouth was bone dry and I constantly needed to pee. I couldn’t sleep. At midnight, the G6 showed my level was high and still rising. I went for a walk, hoping that would bring it down. An hour later I took a correction dose, crossed my fingers and went to sleep.

I’m most in control of diabetes when running

I was up before sunrise. The G6 showed I was high but coming down. I went for a walk, watched the sun come up and took a correction dose. By 7am, my tent mates were eating breakfast. I’d decided to save food for the start line. I planned to take no insulin with it, fearing it would cause my blood to plummet as I ran. I cut my basal rate (the dose the Omnipod administers every five minutes) by 80% to counter the effect of the 20 miles I was about to run through the desert.

My blood shot up

An hour in, my blood spiked at 17mmol (see below). This was because I’d eaten my morning muesli, dried fruit and nuts (pretty much my entire diet that week) with no insulin. This had worked on training runs back home because exercise allows cells to absorb glucose from the blood independently of insulin.

But, because of the excitement of it all and the fact I was moving more slowly than usual to conserve energy, the running alone wasn’t enough to keep me in range. I took a correction dose and made a note to take insulin (albeit a lower dose) with breakfast for the rest of the week. This worked well.

During the MdS, I was most in control of diabetes when I was running. The graphs below bear this out. My blood is in range for the longest periods from about 7.30am, when we started each day. When my level dipped, I took a little glucose, knowing the exertion would cause it to gradually fall until I topped up with more.

I was on the go for several hours a day, taking little insulin in that time. My level shot up whenever I stopped because I had hardly any insulin on board and my cells were no longer absorbing glucose as a result of the exertion. At night, my levels soared. On day five, we had to queue to summit a slope in single file (see the above pic). This caused my blood to spike. It always seemed better just to keep on running.

glucose levels marathon des sables

Heat makes me more insulin sensitive

Sleeping with high glucose levels is difficult. I felt lethargic because my blood was full of glucose, the body’s fuel, and not enough of it was getting to my cells, but I kept having to get up to pee and drink. I was so thirsty. Then there was the worry about what it was doing to my body. It didn’t make for good nights’ sleep.

I lost track of how much insulin, a little at a time, I had on the night of 8 April (day two) after the most beautiful but demanding day’s running of my life. It had little impact. My level was off the scale. The G6 just said ‘high’. At around dawn, exasperated, I took a larger dose (I forget how much). By 6am it was finally falling.

The day of stage three (9 April) was the hottest of the week. I’m told it got up to 45°C in the shade. Not that we saw any shade that day; we ran 23 miles through roasting dunes, salt pans and rockfields. There wasn’t a breath of wind. In the intense heat my blood glucose kept nosediving, after all the extra insulin I’d taken in the small hours to bring it within range.

So, after the third hypo of the day (it was horrible; I was shaking, weak and unbelievably hot), I switched my insulin pump off. This was easier said than done, because I couldn’t read the screen of the Omnipod handset in the glare of the sun. I didn’t take doing it lightly, either, because of the sleepless nights the lack of insulin I’d had on the earlier days had caused.

glucose levels marathon des sables

Running with the insulin pump switched off seemed to work. Thanks to the G6, I could see the trajectory my glucose level was on and pre-empt hypos before it got too low. My level would then rise for an hour or so, fall back and the cycle would begin again.

On stopping on 9 April, I switched the pump back on and gave myself a few extra units of insulin to compensate for the time I’d spent on my feet taking no insulin on board. I still went high that night, but not as high as before. I slept much better, and woke up feeling pretty fresh for the long stage (about 50 miles) on 10 April.

The long stage was like a dream: 50 miles through some of the most breathtaking scenery of the week. I felt more in control of my glucose levels, keeping a close eye on the trajectory it was heading in and taking in food/drink when it was dipping.

The day was spent running and walking through a wide, sandy valley scattered with rock formations and hemmed in by steep hills, before a hillier section that led into a section of dunes. I made the mistake of falling asleep at the penultimate checkpoint. The organisers had put out seats and tents for this purpose, but I’d wanted to keep going. My glucose spiked as a result. I woke at about 2am and got going, crossing the finish line as the sun came up.

I’m very lucky

I managed to keep my levels pretty stable on the rest day (11 April), which I spent trying (and mostly failing) to sleep in the heat and recuperate after the long stage. That evening, knowing we only had one more day of serious running ahead and then the 4 mile charity stage on 13 April, I ate everything in my pack that I wouldn’t need over the following two days. I got the dose wrong, and spent the night with sky high levels. You’d have thought I’d have learned by then.

The final long run of the week, the marathon stage on 12 April, was a joy. Somehow, I managed to keep my levels more or less in range for the day, although they spiked at the end because I was too busy celebrating to spend any more time worrying about them. About seven miles from the finish a small group of kids appeared to give us high fives and cheer us on.

The sight of them brought home to me how lucky I am, even if I do have to walk this endless tight rope between high and low blood sugar levels, knowing that both could kill me or seriously damage my organs. Diagnosis with type 1 diabetes in many parts of Africa is a death sentence. In some countries, you’re not expected to survive longer than six months after diagnosis. We can change that. That’s why I ran the MdS for the charity T1International, which campaigns for diabetics living in parts of the world where there is not adequate access to insulin and other medical supplies (why not donate here?).

I ran full pelt for the final couple of miles of the marathon stage. The finish line had come into view from the top of a rocky ridge we’d been running along for a few miles and was reached down a steep drift of soft sand, followed by about half a mile on the flat. I bounded through that sand like I was on the moon, knowing it would be the last I’d feel beneath my feet for a while. By the time I crossed the line my heart was hammering on my chest and I was gasping for breath.

Race founder Patrick Bauer was on the other side of the line. He hugged me and draped my medal around my neck, as he does for every one of the finishers. Getting the medal felt amazing. I felt like I’d beaten type 1 diabetes and proved all those doubts that had been rattling around my head wrong. But a question kept recurring: would I even have that medal around my neck without the devices stuck to my belly?

Maybe I would. Maybe I wouldn’t. But back in 2005 when I first heard about the MdS, completing this event as a type 1 diabetic was unthinkable to me. Back then, testing my levels meant pricking my fingers and you were given no indication of whether your level was rising or falling. I took two types of insulin in several injections a day.

The G6 allowed me to see not just how much glucose was in my system, but how fast it was falling or rising by just glancing at my wrist. It stayed intact through 140 miles of running, sweat, tears and sand. The Omnipod allowed me to respond to the information the G6 was giving me with the push of a button. Technology was crucial to my success at the MdS.

Disclaimer: I was given a free Dexcom G6 starter pack for the MdS. This is an honest, personal account of my experiences during the MdS. It should not be viewed as advice. If you’re type 1 and considering doing the MdS or a similar event, seek medical (and possibly psychiatric) advice before doing so. 


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