There's a huge sign that the fuel of the US economy is getting cut off

The warning signs of a credit slowdown are beginning to appear.

Late Friday, the Federal Reserve's weekly H.8 report showed that growth in lending for commercial and industrial (C&I) loans has significantly cooled off in recent weeks.

According to Bespoke Investment Group, the annualized quarter-over-quarter growth rate of C&I loans fell to 15.17% based on Friday's data. Just two weeks ago this was 19.34%.

C&I loans are those given to businesses to fund activities from buying equipment to building factories. A slowdown in loans to businesses would most likely translate into lower investment, affecting everything from the labor market to the stock market.

A few weeks ago, we highlighted the latest data from the Fed's Senior Loan Officer Opinion Survey (SLOOS) showing that the people that give out these loans reported tighter lending conditions.

Until now, the three straight quarters of SLOOS responses indicating tighter lending conditions have not shown up in actual credit data. Citi's Tobias Levkovich pointed out in a note last week that credit markets have implied more strength than survey results:

But, the biggest contradiction to the survey results is the trading backdrop that we track in credit markets. For example, Figure 5 underscores the dramatic improvement in high yield funding cost since early February with both Energy and non-Energy debt benefitting. But, investment grade credit spreads also are better, falling 50 basis points since February and are at levels last seen in the summer of 2015, almost running roughshod over the sense that things deteriorated in April.

Levkovich notes, however, is that a change in intentions is typically a leading indicator: A lender has to change their outlook before they can actually stop giving out loans.

"Moreover, the standards survey has provided a respectable 18-month lead on bank loans while various surveys of hiring plans and capital spending budgets show gains being likely in 2016," wrote Levkovich.

From Levkovich's note, here's a comparison of SLOOS lender intentions in blue with actual C&I loan growth six quarters later in black dashes, showing the relationship between lender sentiment and actual future commercial credit growth:

So while intentions have been shifting tighter for some time, this week's H.8 report may be the first sign that intentions may be translating into actions. And while this certainly doesn't mean an end to credit growth overnight, there's reason to believe the lending environment is cooling off.