There is much to be done to prepare for this global epidemic. The sheer size of it means that strategies focused solely on treatment will be far too costly. If nothing changes in the next two decades, India will need to provide chronic care for more than 100 million people with diabetes — close to the entire adult population of Russia.

The solution in India and other developing countries has to include prevention, which means promoting healthy eating and physical activity. It’s not easy: We have by no means succeeded in the United States. In India, it will require better policies that favor fruits and vegetables over refined-food products. One opportunity involves India’s Mid Day Meal Scheme, a program that provides lunches to 120 million children. The program has been tainted by corruption and deadly contamination problems, but as the Indian government addresses these issues, it also has a chance to reshape the dietary habits of many young people. Exercise is the other crucial element. Taking a jog or even walking to work in Indian cities often means choking on exhaust fumes and dodging speeding cars. Creating more sidewalks and bike paths could go a long way.

The second step is providing diabetes patients with medicines that are effective, safe and affordable. On the bright side, for at least a decade, India has manufactured affordable generic insulin. But in recent years, pharmaceutical companies, sensing the potential for profits, have begun to market their products aggressively.

In one major government hospital, I saw lines of pharmaceutical representatives with glossy pamphlets and drug samples waiting to speak with clinicians. Some classes of drugs they’re pushing, such as incretin mimetics — which are injected to lower blood sugars — are very costly, and though they are approved for use in both the United States and India, we don’t know enough about their safety in the long run. They don’t appear to lower blood sugar levels any better than cheaper alternatives like metformin, which comes as a pill and is considered the best first choice for many people with diabetes. In America, expenditures on diabetes medications have soared as newer drugs have been rapidly adopted. India desperately needs to create evidence-based guidelines that take into account cost-effectiveness so that marketing doesn’t drive treatment.

But even the best medicines will not work without a well-functioning health care system. Diabetes care is not a quick fix. You can’t take a pill for 10 days and be cured. It means working with a clinical team to control the disease month after month, year after year. This requires a system that is geared toward chronic care, which in many countries simply doesn’t exist. In India, there is now a call for universal health care. This is encouraging but is a long way from being realized. In the meantime, India could leverage the lessons learned from many successful H.I.V. programs throughout the developing world that have empowered communities to deliver complex clinical services to millions of people at low cost.

In order for policy makers and health officials to bring about these changes, we must change how we think about the disease. Most of us in the West assume we know what the risks and burdens of diabetes are. And if we’re talking about a patient in Kansas City or Tokyo, we’re probably right. But when it comes to diabetes, location is everything, and much of the world is now vulnerable to the most devastating consequences of this disease. If we’re going to be any help at all, we need to make a conceptual shift. We think we know diabetes — and that’s the problem.

Kasia Lipska is an endocrinologist at the Yale School of Medicine.