What are the signs of tongue hardening?

Tongue hard, mainly by four signs: 1, blood viscosity increased, tongue hard, more and slow blood flow, microcirculation changes, local blood supply deficiency, or cerebral blood supply deficiency, can check whether blood lipids, blood sugar, blood pressure is high. 2, ischemic vascular disease, tongue hard, there may be signs of ischemic vascular disease, if ischemic encephalopathy occurs, it will also show this condition. 3, drugs, some drugs such as gentamicin streptomycin can also cause numbness of the tongue and lips, is other situations.4, if there is no swallowing disorder, nerve problems, at the same time to look at the lack of trace elements, such as zinc deficiency can also cause such symptoms.