Worked a shift at UIHC with a resident who got a lactate on a hemodynamically stable asthmatic, and it came back at 4.6. Repeat arterial lactate similar. If you practice drone medicine like this internal medicine resident was doing, you'll be heading down the wrong path ..."pretty much means we need to put a central line in, and I guess start antibiotics."
What the resident didn't know was that asthmatic patients on continuous albuterol nebs will have a type B lactic acidemia. Although the mechanism is not completely understood, β2-agonists are known to stimulate cyclic adenosine monophosphate (cAMP)-mediated glycogenolysis and lipolysis. Hyperglycemia and free fatty acid inhibition of pyruvate dehydrogenase lead to anaerobic metabolism of pyruvate to lactate, thus causing elevated lactate levels. Work of breathing has also been hypothesized to contribute as well.
There are many other causes of type B lactic acidemias, just google them.