Runners: Are you secretly dehydrated?

I was unable to provide blood for a simple blood test two hours after a 10-mile run. This may seem obvious to some of you, but I was shocked.

Some background… I’m about to embark on a journey to lose weight, become fitter and stronger, and generally improve my health and well-being – something I’m calling Super Fit @ 50! As part of that, I’m aiming to get a six pack by Christmas (!) and run a sub-24hr 100-miler next Summer. I’ll be sharing how that goes over the next few months…

So, I wanted to establish a health baseline – something data-based and tangible to measure my progress against. Bloodwork seemed like the best all-round benchmark, so I’ve been using ForthEdge’s home testing kits and online dashboard.

The first kit arrived but I was unable to provide enough blood to fill the two samples – so my results came back as failed tests. That wasn’t a massive surprise: I have poor circulation in my hands, known as Reynaud’s Syndrome. So, I went back to ForthEdge and ordered a home visit phlebotomy draw from a vein, performed by a nurse practitioner – the kind of thing you get from your doctor when you go in for a proper blood test.

Now, I know I probably don’t drink enough water in any given day, but I wasn’t expecting what happened next. The nurse wasn’t able to take a blood sample as my veins were so dehydrated and collapsed. She tried both arms and a foot! I had no idea that my body could be put under so much stress from a lack of fluids following a simple two-hour trail run. Huge learning point.

Obviously, since then, I’ve made a real commitment to drinking plenty of water throughout the day. What’s even more surprising is that, since I’d changed my lifestyle to try and lower my PSA levels and deal with an enlarged prostate earlier this year, I had been drinking a lot more water than before! Anyway, lesson learned.

Since then, I’ve had another blood test. No run beforehand, and I wrapped up warm. Suffice to say, no problem this time. You might already know all this – but I’ve been shocked by the obvious effects of dehydration on my veins after what I thought was a couple of hours of only moderate exertion. And I’ve been running for years, now.

It’s served as a great reminder to not take my body for granted, especially when I consider the amount of stress we place our bodies under by taking part in endurance events.

What about you? Have you ever noticed the hidden effects of dehydration, or had a running-related health scare? Leave me a comment below, or drop me an email on to find out how I can help you set sustainable running goals.


Watch this space! I’ll be blogging about my journey to get Super Fit @ 50 very soon – my attempts to become a fitter, leaner, faster runner and improve my energy levels at home and at work, culminating in (I hope!) a sub-24hr 100-miler next June…



One thought on “Runners: Are you secretly dehydrated?

  1. Hi Andy, thanks for sharing your experience. The data we have at Forth Edge suggests that almost half of all athletes and not drinking enough water. There are two key markers which we test within our Endurance Plus blood profile which can give you an indication of the body’s hydration status – urea and creatinine. Our data shows that 18% of athletes tested for urea were above the normal range with a further 25% in the highest quarter of the range. A very similar pattern was seen for creatinine. So the message loud and clear is that athletes need drink more water especially after heavy training. Best regards & stay healthy, Sarah & The Forth Edge Team


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