Women at Altitude: iron, menstruation, menopause and expeditions

For most of mountaineering’s history, the medical research was done on men, and women were left to extrapolate. That is finally changing, with bodies like the UIAA Medical Commission publishing dedicated guidance on women’s health in the mountains. The honest headline is reassuring: women acclimatize and perform at altitude just as well as men, and sex is not a major risk factor for altitude illness. But a few areas do differ or need planning, and getting them right makes for a safer, more comfortable expedition. We cover them in order of how actionable they are.

Acclimatization works partly by building more red blood cells to carry oxygen in thin air, and that process depends on iron. When iron stores are low, the body cannot mount the full red-cell response, and studies have shown that iron-deficient individuals fail to increase red-cell volume normally on going to altitude. In other words, latent iron deficiency can quietly impair how well you acclimatize. This matters more for women because menstruation is a regular source of iron loss, making iron deficiency more common in women than men. The practical takeaway from mountain-medicine guidance is simple and powerful: check your iron status, meaning ferritin, in the months before a significant expedition, and if it is low, correct it under a clinician’s guidance. Do not simply start high-dose iron on your own, because excess iron carries its own risks; test first, then supplement only if indicated.

Two questions come up here: does altitude affect your cycle, and how do you manage a period in a remote, cold place. On the first, the phase of the menstrual cycle does not appear to change acclimatization or altitude-sickness risk, and there is no strong evidence that altitude itself reliably alters the cycle. What can disrupt or stop periods is the heavy training load and energy deficit of a big expedition, which is worth being aware of. On the second, many women choose to control or suppress their period for an expedition using hormonal methods, which mountain-medicine guidance considers common and safe for this purpose. If you plan to do so, start well before departure, because breakthrough bleeding is common in the first cycles of suppression and takes time to settle. Be aware too that pill timing is hard across time zones and remote days, and that some antibiotics can reduce contraceptive efficacy. Whatever you choose, pack a reliable plan for hygiene and products, including options like menstrual cups that do not depend on resupply.

Estrogen-containing contraception slightly raises the risk of venous blood clots at any altitude. High altitude adds several factors that may compound that risk in theory: the low-oxygen environment itself can nudge the blood toward clotting, and dehydration, cold, and long immobile days add to it. The evidence here is limited, and expert bodies differ. A 2024 UIAA Medical Commission review found that hormonal contraception does not affect acclimatization or altitude sickness and is commonly and safely used to suppress periods, and other sources note no clinically relevant increase in clots among healthy, active, non-smoking women. More cautious guidance from mountain-medicine bodies advises that women with clot risk factors, a personal or family history of thrombosis, or who smoke should avoid combined estrogen contraception at altitude, and that even healthy women consider alternatives for extended stays above about 14,800 feet (4,500 metres). Progestogen-only methods avoid the estrogen-related clot risk entirely.

Reminder: this is general information, not a recommendation for your situation. Decisions about contraception at altitude should be made with your physician, based on your history.

The evidence is encouraging for menopausal and post-menopausal climbers. Fit women in this stage have no known extra risk of altitude sickness, and, as for everyone, the biggest predictor of altitude illness is a previous history of it rather than age or sex. Whether short-term altitude travel changes menopause symptoms simply has not been well studied. The one detail worth knowing concerns hormone replacement therapy: the form of estrogen matters, because oral estrogen may increase clot risk, whereas estrogen delivered through a skin patch is not associated with the same increase. Because age and menopause can shift your cardiopulmonary responses, and therefore acclimatization and performance, sensible training preparation matters as much here as at any age.

Reminder: if you take HRT, discuss it and any extended high-altitude travel with your doctor before you go.

Despite persistent assumptions, sex is not a strong predictor of acute mountain sickness. The single biggest risk factor, by a wide margin, is having had altitude sickness before, and that holds regardless of sex or age. Hormonal contraception does not appear to change the risk either. So the prevention playbook for women is exactly the one everyone should follow: ascend gradually, build in acclimatization days, know the early symptoms, and descend if they worsen. Our altitude acclimatization guide covers the protocol in full, and it applies equally to everyone on the team.

This is the one area we will not try to guide you through, because it is individual and belongs with your obstetrician. In general terms, medical guidance urges caution about strenuous exertion and high altitude in pregnancy, especially later on, and lists specific contraindications such as pregnancy-related hypertension, impaired placental function, growth restriction, and maternal heart or lung disease. Beyond the physiology, remoteness from obstetric care, the raised risk of falls from a shifting center of gravity and greater joint laxity, and even harness fit all add reasons for caution. If you are pregnant or may become pregnant and are planning altitude travel, please seek personalized medical advice first.

Reminder: altitude travel during pregnancy should only follow personalized advice from your obstetric care provider.