While most international companies are suffering from the stronger dollar, Novo Nordisk (NYSE:NVO) is benefiting since the diabetes specialist reports its sales in the Danish kroner. Sales increased 20% in the third quarter and earnings per share rose 32% year over year. But in local currencies, the sales growth wasn't nearly as impressive, with sales up just 8% year over year.

Of course, 8% growth isn't too shabby, especially since rival Sanofi (NYSE:SNY) reported that sales of its diabetes products fell 6.6% year over year at constant exchange rates in the third quarter. Sanofi is being hurt by lower U.S. sales of its basal insulin Lantus, which saw third-quarter sales fall 10.8% year over year at constant exchange rates.

Novo Nordisk's basal insulin Levemir seems to be the cause of some of that decline. In the third quarter, North American sales of Levemir increased 14% year over year in local currencies. As of August, Levemir's U.S. market share increased to 24% of prescriptions, despite Sanofi's launch of Toujeo in April.

Victoza continues to help drive Novo Nordisk's revenue growth with a 20% year-over-year increase in sales in local currencies. While Victoza has new competition from GlaxoSmithKline's Tanzeum and Eli Lilly's (NYSE:LLY) Trulicity, which both launched fairly recently, the GLP-1 drug class is growing, making up for the slightly lower market share. AstraZeneca's Byetta and Bydureon have suffered more than Victoza.

Besides Levemir and Victoza, the rest of Novo Nordisk's franchises remain relatively slow growers. Top-selling NovoRapid, for instance, grew at 3% year over year in local currencies. Novo Nordisk's hemophilia drugs grew at the same 3% rate as well. Fortunately, Levimir and Victoza combined are 35% of sales, so they can move the revenue needle with their double-digit growth.

Looking forward
Management kept its 2015 guidance for revenue growth in local currencies at a 7% to 9% year-over-year growth, but increased its 2015 guidance for operating profit growth; the company now expects to see 20% growth in local currencies compared to the previous guidance of 19%.

Next year won't be quite as good for the bottom line. Management gave preliminary guidance for 2016 to expect sales growth in the mid- to high-single-digits in local currencies. Operating profit will grow by the same amount, adjusted for the partial divestment of its life sciences IT consulting group and the income from out-licensing its inflammation assets, which both occurred this year.

Investors should keep an eye on Novo Nordisk's newest insulin, Tresiba, which was approved in September and will be launched in early 2016. Sanofi expects its diabetes sales for 2015-2018 to decline at an average annualized rate of between 4% and 8% at constant exchange rates, and Eli Lilly's management also talked about a slowing insulin market on its third-quarter call.

Early sales of Tresiba and whether Sanofi and/or Eli Lilly are losing market share will be key to whether Novo Nordisk can meet its goal of 7% growth in volume of insulin products. Sales growth of the products is expected to trail that number due to falling prices.

Brian Orelli has no position in any stocks mentioned. The Motley Fool recommends Novo Nordisk. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.