Norway is, in general, a very healthy place and no special precautions are necessary when visiting. The biggest risks are likely to be viral infections in winter, sunburn and insect bites in summer, and foot blisters from too much hiking.
The World Health Organization (WHO) recommends that all travellers should be covered for diphtheria, tetanus, measles, mumps, rubella and polio, regardless of their destination.
If you do fall ill while in Norway you will be very well looked after as health care is excellent.
Most medications are available in Norway, but may go by a different name than at home, so be sure to have the generic name, as well as the brand name. If carrying syringes or needles, be sure to have a physician's letter documenting their medical necessity. For minor illnesses, pharmacists can dispense valuable advice and over-the-counter medication.
Like almost everything else, medical care can be prohibitively expensive in Norway and insurance is a must.
Tap water is always safe to drink in Norway, but it's wise to beware of drinking from streams, as even the clearest and most inviting water may harbour giardia and other parasites. For extended hikes where you must rely on natural water sources, the simplest way of purifying water is to boil it thoroughly; at high altitude water boils at a lower temperature, so germs are less likely to be killed. Boil it for longer in these environments (up to 10 minutes).
If you cannot boil water it should be treated chemically. Chlorine tablets (Puritabs, Steritabs or other brands) will kill many pathogens, but not giardia and amoebic cysts. Iodine is more effective in purifying water and is available in tablet form (such as Potable Aqua). Too much iodine can be harmful.
Norway's perilously cold winters require that you take the proper precautions if travelling at this time. Even on a hot day in the mountains, the weather can change rapidly – carry waterproof garments and warm layers, and inform others of your route.
Hypothermia starts with shivering, loss of judgment and clumsiness. Unless rewarming occurs, the sufferer deteriorates into apathy, confusion and coma. Prevent further heat loss by seeking shelter, warm dry clothing, hot sweet drinks and shared body warmth. Acute hypothermia follows a sudden drop of temperature over a short time. Chronic hypothermia is caused by a gradual loss of temperature over hours.
Frostbite is caused by freezing and subsequent damage to bodily extremities. It is dependent on wind-chill, temperature and length of exposure. Frostbite starts as frostnip (white, numb areas of skin) from which complete recovery is expected with rewarming. As frostbite develops, the skin blisters and becomes black. Loss of damaged tissue eventually occurs. Wear adequate clothing, stay dry, keep well hydrated and ensure you have adequate calorie intake to prevent frostbite. Treatment involves rapid rewarming. Avoid refreezing and rubbing the affected areas.
In northern Norway, the greatest nuisances are the plagues of blackflies and mosquitoes that swarm out of tundra bogs and lakes in summer. Fortunately, malaria is unknown, but the mental risks can't be underestimated, as people have literally been driven insane by the ravenous hordes. Midsummer is the worst, and regular mosquito coils and repellents are scarcely effective; hikers must cover exposed skin and may even need head nets to keep the little buggers from making kamikaze attacks on eyes, nose, ears and throat. If you're camping, a tent with mosquito netting is essential.
Most people get used to the mosquito bites after a few days as their bodies adjust and the itching and swelling become less severe. An antihistamine cream should help alleviate the symptoms. Use a DEET-based insect repellent.
Rabies, caused by a bite or scratch by an infected mammal, is found in Svalbard and (occasionally) in eastern Finnmark. Dogs are a noted carrier, but cats, foxes and bats can also be infected. Any bite, scratch or even lick from a warm-blooded, furry animal should be cleaned immediately and thoroughly. Scrub with soap and running water, and then apply alcohol or iodine solution. If you've been infected by a rabid animal, medical help should be sought immediately.