After it acquired six companies and started a joint venture in the past year-and-a-half, I kind of figured that Inverness Medical Innovations (AMEX:IMA) would take a break. Boy, was I wrong.

Monday evening, Inverness announced that it's acquiring HemoSense (AMEX:HEM) in an all-stock deal. The ratio of shares traded in the deal represents a 37.5% premium for HemoSense shareholders, based on the average trading prices of both companies over the five trading days before the announcement.

There's a good reason why Inverness is using its stock to pay for the $167 million deal; following its recent acquisitions of Biosite and Cholestech (NASDAQ:CTEC), it's running low on cash and credit.

HemoSense's handheld blood coagulation system, INRatio, uses a small monitor and disposable test strips to determine how quickly patients' blood is clotting. That information is critical for patients taking anti-coagulation drugs containing warfarin, such as Bristol-Myers Squibb's (NYSE:BMY) Coumadin. Warfarin is notoriously hard to regulate, because it interacts with food and other medications.

HemoSense has increased sales substantially in the last year. For the most recent quarter, sales of meters rose 99% year over year, while sales of the test strips used in the machines increased 102%. I really like HemoSense's business model of selling equipment, then having reoccurring sales of consumables to its new customers. For investors, it's also easier to see where sales are headed in future quarters, since they're driven by placement of machines.

While the sales increases are certainly impressive, Inverness may have overpaid for HemoSense, which failed to produce a profit from those stellar revenue gains. The purchase price of $167 million represents 10 times HemoSense's revenues for the trailing 12 months. Inverness will have to do some serious cost-cutting to fatten margins in order to justify the price. Some of that synergy may come from combining Hemosense's salesforce with Inverness's newly acquired Quality Assured Services, which sells three coagulation instruments.

The biggest problem with the most recent acquisition is that Inverness may be spreading itself too thin. There are only so many managers who can work on lowering margins in the new companies. By purchasing so many companies so quickly, Inverness risks becoming unable to take full advantage of the synergies between its new subsidiaries, and thus squandering its shareholders' equity.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool's disclosure policy is thicker than water.