According to new Diabetes Atlas figures released by the International Diabetes Federation, 366 million people on the planet now have diabetes. Yikes! Talk about a large market.

And better yet -- for companies that sell treatments, not patients or governments that have to pay $465 billion annually -- the number of people with diabetes continues to grow. People moving into the middle class in developing nations has been a major contributor to the upward trend.

Competition galore
 While having lots of people that need drugs is a good thing for companies, there's lots of competition for those patients.

Type 2 diabetics -- a vast majority of the new diabetes patients -- usually start on metformin, a generic drug, progress to brand name oral drugs before eventually taking drugs that have to be injected.

After GlaxoSmithKline's Avandia ran into side-effect problems, the oral branded-drug space has become dominated by Merck's (NYSE: MRK) Januvia and Janumet, a combination of Januvia and metformin. Takeda sells Actos, another popular oral medication, but you'll have to head to the Tokyo Stock Exchange to invest in the company.

The established leaders make it extremely hard for newcomers to break in. Two years after Bristol-Myers Squibb (NYSE: BMY) and AstraZeneca (NYSE: AZN) got Onglyza approved, sales of Onglyza and its metformin combo pill, Kombiglyze, still pale in comparison to sales of Merck's franchise.

If companies are going to break into the oral medication space, they'll have to find a way to differentiate themselves. Bristol-Myers and AstraZeneca seemed to have found that in dapagliflozin, which works through a different mechanism. But potential side effects could derail the drug.

For injectable drugs, the space is more open. Sure, they're not the first choice for most patients -- few people like to stick themselves with needles -- but diabetes is a progressive disease, and patients eventually need more glucose control than oral medications can provide. Type 2 diabetics eventually progress to insulin such as Sanofi's Lantus, Novo Nordisk's (NYSE: NVO) NovoLog, and Eli Lilly's (NYSE: LLY) HumaLog, but I have a hard time seeing much growth there. Except of the potential to remove needles altogether -- which MannKind (Nasdaq: MNKD) is working on -- for the most part, technical advances in insulin have already been made.

The sweet spot is between oral medications and insulin, especially if the drug can be injected less frequently than insulin. Amylin Pharmaceuticals (Nasdaq: AMLN) and Eli Lilly developed Byetta, but it had to be injected twice a day, so sales never really took off. Novo trumped Byetta with a once-daily drug, Victoza, in the same class. Half as many needle pokes not only allowed the company to take market share from Byetta, but it also grew the use of the entire class of drugs.

That should be good news for Amylin and Eli Lilly as they wait for the FDA to approve their once-weekly version of Byetta called Bydureon. Alkermes, which contributed the extended-release technology, will also benefit from the launch.

More a matter of "where" than "how much"
 While the global incidence of diabetes is increasing substantially, I'm not sure sales will keep the same pace. If much of that growth is coming from increases in developing countries' middle classes, the new patients may not be able to afford the drugs at prices that drugmakers are accustomed to. China has cracked down on ballooning drug costs for its citizens using price caps; expect other countries to follow suit.

Even with that caveat, there's still plenty of growth available. Another study predicted the potential for an additional 8 million cases of diabetes by 2030 in the U.S. alone as the obesity rate potentially climbs to 50%.