Tokyo enjoys an excellent standard of public hygiene and health (stress-related ailments notwithstanding).
The level of care in Tokyo is high, but English is only reliably spoken at certain clinics and hospitals. Your accommodation may be able to help; you can also use the city's emergency translation service.
Every Tokyo neighbourhood has at least one primary care clinic. Called naika (内科), these are often small – sometimes run by just one doctor – and are considered the first point of contact for common, non-urgent complaints, like rashes, sinus infections, gastric upsets and the like. For additional care, the doctor can refer you to a specialist.
There is no requirement in the Japanese system to register with a particular primary care doctor or clinic. Most naika accept walk-ins; in fact, many do not take appointments. Be prepared to wait and note that most close for several hours during the early afternoon. Unfortunately, English can be hit-or-miss at neighbourhood naika.
Tokyo has a few clinics that cater to the expat community and thus have English-speaking (and often foreign-trained) doctors, nurses and staff. Bear in mind that the cost of healthcare at these facilities may be higher than that of a typical naika.
Reliable options include:
Primary Care Tokyo Appointments accepted and recommended, but walk-ins will be seen.
Tokyo Medical & Surgical Clinic Appointments required; however, walk-ins needing urgent care will be accepted. Has in-house English-speaking specialists. Pricier than most.
For dental concerns, see English-speaking Trust Dental Clinic. They're very popular and often fully booked, but will try to accommodate those in need of urgent care.
St Luke’s International Hospital Tokyo's most foreigner-friendly hospital, with English-speaking doctors and translation services provided. Walk-ins accepted for primary care (8.30am to 11am weekdays) and paediatric care (8.30am to 11am and 6.45pm to 9.45pm weekdays); appointments are required for specialist care. Has 24-hour emergency care.
Common pharmacy chains include Matsumoto Kiyoshi (マツモトキヨシ), Tomod's (トモズ) and Tsuruha Drug (ツルハドラッグ). Almost every train station will have one nearby. Neighbourhood pharmacies are generally open 10am to 9pm but you can find 24-hour ones in big hubs like Shinjuku and Shibuya.
Pharmacies in Japan carry very few recognisable foreign brands (Tylenol, a brand of paracetamol, is an exception). Local substitutes of common medication such as ibuprofen and cough syrups are available, though the dosages may be less than what you're used to. For stronger doses, you'll need to see a doctor for a prescription. Packaging is often evocative, but double-check with the staff; some may speak some English, otherwise miming is usually effective.
Only some pharmacies carry clotrimazole (to treat yeast infections), which is kept behind the counter (you'll have to ask for it); better to pack your own.
Pharmacies are also the place to pick up condoms, pregnancy tests, feminine hygiene products and nappies.
Tap water is safe to drink in Tokyo.
The only insurance accepted at Japanese clinics and hospitals is Japan-issued health insurance; however, they cannot refuse treatment for lack of insurance. For any medical treatment you'll have to pay up front (credit cards are accepted at hospitals and may or may not be accepted at local clinics) and apply for reimbursement when you get home. Even paid in full, the cost of medical care in Japan is low compared to countries like the US.
Clinics, dentists and hospitals with a special interest in serving Tokyo's expat community may have arrangements with some of the larger, global providers; you will need to check with your provider in advance. These will also be able to provide claim forms in English.
No vaccines are required for travel to Japan.