What you're looking at is a design mockup of Body+, not a live product. Nothing here is for sale, no formula you build will be made, and the numbers you'll see are illustrative.
Fifteen to forty days on snow at altitude, four to six hours a day. Ferritin falls while haemoglobin stays normal, and a standard panel checks only the one that moves last. Here's the load a ski season actually creates, and the formula it implies.
Not because you ski. Because of four specific things that altitude, cold, eccentric load and consecutive days do to you.
Above 2,000 metres arterial oxygen saturation falls and ventilation rises to compensate, which increases respiratory water loss in air that is already near zero humidity. Cold blunts thirst exactly when losses climb. Sweat sodium concentration varies enormously person to person, so replacing volume with plain water while ignoring the solute is the usual reason cramping appears on day three of a trip rather than day one. Stored iron depletes before circulating haemoglobin falls, so a standard panel can miss a depleted skier entirely.
Descent is dominated by eccentric quadriceps work, which produces more muscle damage per unit of perceived effort than concentric work. Soreness peaks twenty-four to forty-eight hours later, which lands on the next consecutive ski day rather than a rest day. The load doesn't feel hard in the moment—you're riding a lift between runs—so the mismatch between what it felt like and what it cost is where most skiers misjudge recovery need. Joint load from repeated impact and edge work accumulates across consecutive days.
Cold shifts fuel use toward carbohydrate and raises energy expenditure through shivering and through carrying equipment. Four to six hours on snow, much of it at low perceived intensity, still represents sustained turnover—but hunger cues are blunted in cold the same way thirst is, so intake falls when demand is elevated. The combination of altitude, cold and consecutive days creates a deficit that compounds across a trip, and it shows up as fatigue on day four or five rather than day one.
Ultraviolet exposure at altitude on snow is roughly double sea level, which raises oxidative load. The ski season falls entirely within the months when cutaneous synthesis at European latitudes is negligible—October through March—so time outdoors contributes nothing to status. The assumption that mountain sport solves the problem is the failure: you are outside, in intense UV, and making none of the vitamin the sun is supposed to provide. Antioxidant demand tracks with UV dose and with the repeated eccentric work of descent.
This is the cohort prior: what fifteen to forty days on snow at altitude implies before we see a panel. Three of the four numbers above are guesses, and a measured ferritin is what replaces the guess that costs most if we get it wrong.
Refine this with my answers* Claims shown are limited to authorised structure/function statements. Iron contributes to normal formation of red blood cells and haemoglobin. Magnesium contributes to normal muscle function and to the reduction of tiredness and fatigue. Magnesium contributes to normal energy-yielding metabolism. Body+ products are food supplements and are not intended to diagnose, treat, cure or prevent any disease.
We will not push iron at you on the strength of a quiz. Excess supplemental iron in someone already replete is pro-oxidant, interferes with zinc and copper handling, and no amount of self-reported ski days tells us where your stores sit. Of two estimates, ferritin is the one we would rather measure than guess—and the one a standard panel does not check.
Altitude lowers arterial oxygen saturation, cold raises metabolic demand, and four to six consecutive days on snow is sustained turnover even when it doesn't feel hard. The marker that falls first is the one a standard panel doesn't check.
Ferritin falls while haemoglobin stays normal The body protects circulating haemoglobin at the expense of stored iron, so ferritin—the storage marker—falls first, sometimes for months, while haemoglobin stays inside its reference band. A skier in that state is measurably not anaemic and simultaneously operating on depleted stores. Altitude compounds it: when arterial saturation is already compromised at 2,000 metres, even a marginal deficit in oxygen-carrying capacity costs more than it would at sea level. The combination of reduced partial pressure, sustained turnover across consecutive days, and training inflammation all draw stores down faster than circulating markers reveal.
What a standard panel shows, and misses A full blood count reports haemoglobin and will tell you if you are anaemic. It will not tell you that your stores are running low until haemoglobin itself begins to fall, which is a late signal. A skier can return a haemoglobin reading comfortably inside the reference range—140 g/L, say—and still be operating on ferritin in the low teens, which is functionally depleted for someone training at altitude across consecutive days. The standard read says "your bloods are fine"; the reality is that the deficit has been building for weeks and the test you were given does not look at the marker that moves first. This is a documented case in our own research: an endurance athlete, ferritin depleted mid-block, haemoglobin still nominally in range. See the evidence section for what that research did and didn't show, including the honest limits of the dataset size.
What we therefore refuse to do We will not push iron at you on the strength of a quiz. Excess supplemental iron in someone who is already replete is not a neutral act—it is pro-oxidant, it interferes with zinc and copper handling, and no amount of self-reported ski days or training volume tells us where your stores actually sit. The formula you see here is deliberately conservative for exactly that reason. If you have a measured ferritin, we will use it. If you do not, we would rather underestimate the need than guess high and risk harm. This is a commercial cost to us—we could sell you more—but it is the only honest position when the marker we care about is the one a standard panel does not check.
Haemoglobin and vitamin D, ideally before the season starts—October or November—and again at 8–12 weeks. Haemoglobin tells you if the deficit has progressed to anaemia; vitamin D confirms what the calendar already implies, which is that cutaneous synthesis at European latitudes between October and March is negligible regardless of time outdoors. Fasting glucose if training load is high and fuelling across consecutive days is inconsistent, which is common when cold blunts hunger exactly as demand climbs. Retest at 8–12 weeks: what turns a formula into a loop instead of a purchase.