The present study investigated the effect of garlic (G) on serum, liver, renal and cerebral parameters of rats with chronic intermittent hypoxia (CIH) combined with diabetes mellitus (DM). A total of 32 rats were divided into eight groups, with 4 rats/group. A total of three models were established, including CIH, DM and CIH‑DM, and an additional healthy control (C) group. Rats in C‑G, CIH‑G, DM‑G and CIH‑DM‑G groups were injected with a G extract daily. Serum, liver, renal and cerebral parameters were detected. The results demonstrated that the rats' weight increased gradually, but at a slower rate in the CIH, DM and CIH‑DM groups compared with the healthy rats. Blood glucose increased in the DM and CIH‑DM groups compared with the healthy control group, while insulin level increased in the CIH group, but decreased in the DM and CIH‑DM groups, resulting in increased homeostatic model assessment of insulin resistance (HOMA‑IR) value in the CIH group, compared with healthy controls. Serum thiobarbituric acid reactive substances (TBARS), glutathione S‑transferase (GST), uric acid (UA), urine protein (UP), total cholesterol (TC), triglycerides (TG), total lipids (TL), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and acid phosphatase (ACP) increased in the CIH, DM and CIH‑DM groups, while albumin and superoxide dismutase (SOD) decreased in all model groups compared with healthy controls. Nitric oxide (NO) increased in the DM and CIH‑DM groups but decreased in the CIH group, compared with the control group. Glutathione peroxidase (GSH‑Px) increased in the CIH group but decreased in the DM and CIH‑DM groups, compared with the control group. Glutathione reductase (GR) increased in the DM group but decreased in the CIH and CIH‑DM groups, compared with the control group. Liver TBARS and GST increased, while AST, ALT, LDH, ALP, ACP, catalase activity (CAT) and SOD decreased in the CIH, DM and CIH‑DM groups, compared with the control group. Liver GSH‑Px decreased in the DM and CIH‑DM groups, compared with the control group. Renal TBARS in the DM and CIH‑DM groups increased compared with the control group. Renal GST increased while CAT and SOD decreased in the CIH, DM and CIH‑DM groups, compared with the control group. Cerebral TBARS increased in the CIH, DM and CIH‑DM groups and LDH increased in the DM and CIH‑DM groups, compared with the control group. Cerebral LDH in CIH decreased compared with the control group. G treatment improved weight gain, blood insulin and HOMA‑IR in the DM and CIH‑DM groups, reduced blood glucose in the DM and CIH‑DM groups, and insulin and HOMA‑IR in the CIH group, compared with the respective G‑untreated groups. G treatment increased serum SOD in CIH‑G, DM‑G and CIH‑DM‑G groups, GSH‑Px and albumin in the DM‑G and CIH‑DM‑G groups, and GR in the DM‑G group, compared with the respective G‑untreated groups. G treatment decreased serum TBARS, UA, UP, TC, TG, TL, AST, ALT, LDH and ACP in the CIH‑G, DM‑G and CIH‑DM‑G groups; N...