Anyone with anything bad to say about Nvidia (NVDA 3.51%) over the past four months has probably had to eat their words. The stock has almost doubled in value since the new year, an impressive feat for a mega-cap blue chip stock.

I'll admit it doesn't feel good going against the market, but there is evidence that Nvidia's epic run could soon end. There are already warning bells ringing that investors should listen to.

Excitement over artificial intelligence has Nvidia stock soaring, but here are some things to consider before the company reports earnings in a few weeks.

Nvidia's business is slowing down

Nvidia is a semiconductor stock -- the company specializes in discrete graphics processing units (GPUs) designed for heavy computing workloads. Nvidia's chips are favored in gaming, data centers, autonomous driving, cryptocurrency mining, and, of course, artificial intelligence (AI). Some believe that the  AI market could be worth $41 trillion by 2030, which makes it a tremendous opportunity for Nvidia. The hype around AI in 2023 explains much of the stock's recent momentum.

But Wall Street might be looking too far ahead. Nvidia's business showed signs of slowing down for more than a year now. Revenue growth peaked in early 2021, and inventories have steadily stacked higher, almost quadrupling over the past three years.

NVDA Revenue (Quarterly YoY Growth) Chart

NVDA Revenue (Quarterly YoY Growth) data by YCharts

Many experts fear that a recession is about to rock the economy, which won't help Nvidia's business find traction. An inventory glut and slowing demand could mean downward pressure on Nvidia's bottom line if the company cuts prices to move products.

Is AMD's guidance a preview for later this month?

One of Nvidia's archrivals gave a potential preview of what's to come when Advanced Micro Devices (AMD -2.38%) reported its first-quarter earnings. The company guided for $5.3 billion in revenue for the second quarter, a 19% year-over-year decline. Management pointed to weakness in its client, gaming, and data center segments as the reason for the anticipated drop.

Just because AMD sees some weakness in its business doesn't mean Nvidia will. But Nvidia has shown signs of slowing down for multiple quarters now, so it seems that massive guidance from the company would be a surprise.

Semiconductor companies are cyclical, which means they're sensitive to economic trends. The long-term potential for AI might be great, but the existing business can stumble if a softening economy reduces demand for Nvidia's products.

The stock leaves zero margins for error

Nvidia's stock's remarkable run put investors in a situation where they could get burned when earnings come out later this month. Analysts have begun factoring AI-related growth into Nvidia, raising expectations for long-term earnings growth to their highest levels in years.

But Nvidia's valuation has more than made up for that. Its price-to-earnings ratio (P/E) rose to more than 160, its highest by a long shot and nearly triple its average over the past five years.

NVDA PE Ratio Chart

NVDA PE Ratio data by YCharts

Stock valuations reflect the stock market's expectations for a business's performance. Such a high valuation means that investors expect perfection out of Nvidia. If earnings fall short, the consequences could be a violent rerating of the stock's valuation, burning anyone who bought shares at these high prices.

Maybe Nvidia knocks it out of the park, and the stock continues roaring higher -- it wouldn't be the first time I was wrong. But the canary in the coal mine is singing a tune, and investors should at least listen.