Yes, travel insurance is essential for a trip to Kathmandu, and doubly so if trekking at altitude features anywhere on the itinerary. Kathmandu itself holds the country's most capable hospitals and functions as Nepal's real medical hub, but most of what makes insurance genuinely necessary here happens well outside the city, on trekking routes toward Everest Base Camp or through the Annapurna region, where altitude and remoteness turn a routine injury into a logistics problem.
Helicopter evacuation is the core of the insurance question for anyone trekking above the Kathmandu Valley: routes through the Khumbu and Annapurna regions often sit far enough from a road that a helicopter is the only realistic way to bring someone back to Kathmandu quickly. Confirm your policy explicitly names helicopter evacuation and high-altitude trekking, including any altitude ceiling in the wording, since a policy silent on either point can leave a genuinely serious situation uncovered exactly when it matters most.
Nepal sits in an active seismic zone, and the 2015 earthquake remains a real part of the country's recent history; this is a geological fact of the region rather than a current warning, but it is worth having trip-disruption cover that accounts for infrastructure being affected by events outside anyone's control. Monsoon season, roughly June through September, brings heavy rain that can trigger landslides and disrupt both road travel and the mountain flights that connect Kathmandu to trekking gateway towns like Lukla.
Check whether your existing health cover extends abroad and specifically to Nepal before relying on it, since trekking and high-altitude activity are exactly the kind of cover many home policies quietly exclude. Keep any clinic paperwork, guide or permit documentation, and receipts for helicopter transport, since claims involving mountain evacuation depend heavily on documentation gathered at the time rather than reconstructed afterward.