What Causes Palpitations While Suffering From Depression And Anxiety?

Hi, I’m wondering if you could help me. My dad suffers with depression, bipolar, anxiety, agoraphobia and alcholism. He takes a combination of tablets including lithium and drinks 11 cans of Carling every night. He doesn’t particularly eat until the evening and drinks water up until he starts his nightly routine of drinking. He previously had blood tests to check his liver every 3 months but due to changing doctors who won’t do home visits because he’s “not elderly” despite the fact he’s not left the house in 3 years means these have not been done regularly. He’s had his first one in two years recently and his Gamma GT reading was 160. As it was a councillor who found this reading, she was unsure what it meant and he’s getting a bit frantic about it. He has also recently had a change in tablets for his mental health problems and is also suffering with a bad chest and heart palpitations. Please could you shed a bit of light around the GGT reading and what it means? Thank you.