Amphastar Pharmaceuticals, Inc.'s (NASDAQ:AMPH) price-to-earnings (or "P/E") ratio of 13.2x might make it look like a buy right now compared to the market in the United States, where around half of the companies have P/E ratios above 17x and even P/E's above 31x are quite common. However, the P/E might be low for a reason and it requires further investigation to determine if it's justified.

Amphastar Pharmaceuticals certainly has been doing a good job lately as its earnings growth has been positive while most other companies have been seeing their earnings go backwards. One possibility is that the P/E is low because investors think the company's earnings are going to fall away like everyone else's soon. If you like the company, you'd be hoping this isn't the case so that you could potentially pick up some stock while it's out of favour.

Does Growth Match The Low P/E?

The only time you'd be truly comfortable seeing a P/E as low as Amphastar Pharmaceuticals' is when the company's growth is on track to lag the market.

Retrospectively, the last year delivered an exceptional 67% gain to the company's bottom line. Pleasingly, EPS has also lifted 5,899% in aggregate from three years ago, thanks to the last 12 months of growth. Accordingly, shareholders would have probably welcomed those medium-term rates of earnings growth.

Shifting to the future, estimates from the six analysts covering the company suggest earnings should grow by 16% each year over the next three years. With the market only predicted to deliver 10.0% per annum, the company is positioned for a stronger earnings result.

In light of this, it's peculiar that Amphastar Pharmaceuticals' P/E sits below the majority of other companies. It looks like most investors are not convinced at all that the company can achieve future growth expectations.

The Final Word

Using the price-to-earnings ratio alone to determine if you should sell your stock isn't sensible, however it can be a practical guide to the company's future prospects.

We've established that Amphastar Pharmaceuticals currently trades on a much lower than expected P/E since its forecast growth is higher than the wider market. There could be some major unobserved threats to earnings preventing the P/E ratio from matching the positive outlook. It appears many are indeed anticipating earnings instability, because these conditions should normally provide a boost to the share price.

It is also worth noting that we have found 2 warning signs for Amphastar Pharmaceuticals that you need to take into consideration.

You might be able to find a better investment than Amphastar Pharmaceuticals. If you want a selection of possible candidates, check out this free list of interesting companies that trade on a low P/E (but have proven they can grow earnings).

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This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.