Finally, Cramer looked into Esperion Therapeutics, a small-capitalization, development-stage biotechnology company that just issued a large secondary offering.
"When a little company with a red-hot stock does a big equity offering, that tends to be a pretty strong signal that you need to get more cautious," Cramer warned.
Amid years of wild trading, Esperion, which focuses on treatments for high cholesterol, has issued several stock offerings, usually following promising news about its drugs.
"First, you have to remember, as an early-stage biotech with no drugs on the market, no earnings, and no sales, this stock trades purely on how people feel about its longer-term prospects," Cramer explained. "The bottom line is that early-stage biotech stories are inherently risky. The last time Esperion did a secondary offering after announcing strong data, its stock ended up losing 90 percent of its value before it bottomed. I'm not saying that'll happen again. I just think you need to be careful, and while the company has definitely improved and it's farther along and we love stage 3, stocks like Esperion? Well, I've learned my lesson. I think they're too risky for me to recommend on Mad Money."
In response to CNBC's request for comment, an Esperion spokesperson emphasized the company's announcement of positive top-line results in its Phase 2 study of a treatment for inflammation associated with cardiovascular disease.
"Based on the positive reaction to this news, the company made the decision to opportunistically conduct a financing, helping to further strengthen their financial position as they progress further in to Phase 3 development and approval. As importantly, the financing provided large, long-term, institutional investors the opportunity to build substantial ownership positions in Esperion," the spokesperson wrote. "It's also important to highlight that the management team of Esperion continues to be "fully-invested" in the current and future success of the bempedoic acid franchise. We are large and long-term holders of Esperion stock and options."