Relative contraindications are inferred from partial research evidence and indirect mechanisms, suggesting that the ketogenic diet (KD) may pose risks in certain situations. These include acute pancreatitis, acute liver failure, advanced chronic kidney disease, use during propofol administration, and familial hypercholesterolemia. Unlike absolute contraindications, KD may still offer potential benefits for some individuals under these relatively contraindicated conditions. However, relevant research and clinical experience are currently insufficient. Therefore, until sufficient safety evidence is available, these scenarios should be regarded as contraindications requiring extreme caution.
The KD is not advisable for patients with acute pancreatitis during the acute phase. The pancreas plays a key role in fat digestion, and a high fat load significantly increases its secretory burden, which delays recovery from inflammation and raises the risk of necrosis and infection. Although dietary structure may be re‑evaluated during the remission phase, KD during the acute phase clearly does more harm than good.
In patients with acute liver failure, massive hepatocyte necrosis severely impairs fat metabolism. There is currently no clinical evidence supporting the safety or efficacy of KD at this stage, so it should be considered contraindicated. Patients with chronic fatty liver or metabolic‑associated steatohepatitis may benefit from KD, but their pathological mechanisms are completely different from those of acute liver failure.
Patients with advanced chronic kidney disease (G3b–G5) have reduced ketone body clearance and impaired electrolyte regulation. During the KD adaptation period, substantial losses of water, sodium, potassium, and magnesium, along with a metabolic acid load, may quickly exceed the kidneys’ compensatory capacity, leading to severe cardiac arrhythmias, volume disorders, and acidosis.
Patients with familial hypercholesterolemia exhibit highly heterogeneous lipid responses to KD, with some individuals showing a marked increase in LDL‑C; long‑term cardiovascular safety remains inconclusive. Propofol inhibits fatty acid oxidation, and its combined use with KD increases the risk of severe metabolic complications. Both represent important relative contraindications.