Who Should Not Do Keto: Contraindications and Drug Interactions
A ketogenic diet is not suitable for people with rare inherited disorders of fat metabolism, pyruvate carboxylase deficiency, or porphyria. The warning about SGLT2 inhibitors is especially serious, because dangerous ketoacidosis can occur when they are combined with keto; insulin and sulphonylureas can cause hypoglycaemia on keto if the dose is not adjusted. Relative contraindications are acute pancreatitis, acute liver failure, advanced chronic kidney disease, familial hypercholesterolaemia, and the use of propofol. This guide draws mainly on a 2026 narrative review in Annals of Medicine, alongside the American Diabetes Association (ADA) Standards of Care 2026, which are written for diabetes care, and current prescribing information. The review does not assess the evidence systematically, and many of its classifications rest on case reports and mechanisms. If you take medication or have a chronic condition, agree your keto start with your doctor first and do not change a dose on your own.
Absolute contraindications: who must not follow keto
Absolute contraindications are rare but serious. The review lists inherited disorders of fatty acid oxidation and carnitine metabolism (such as primary carnitine deficiency, CPT1 and CPT2 deficiency, and MCAD, LCHAD and VLCAD deficiency), pyruvate carboxylase deficiency, and porphyria. With fatty acid oxidation disorders, the body cannot use fat adequately for energy. In pyruvate carboxylase deficiency, impaired gluconeogenesis leaves it dependent on dietary glucose. In porphyria, low-carbohydrate eating can promote acute attacks. Many of these disorders show up early in life, but milder forms and porphyrias can go unrecognised for a long time. Anyone with a family history of metabolic disease or a suspected undiagnosed metabolic disorder should have this checked before starting.
Relative contraindications: best treated as absolute for now
Relative does not mean safe as long as a doctor is involved. The review classifies these conditions this way because research and clinical experience are lacking, and says it may be safest to treat them as absolute contraindications until better data exist. In acute pancreatitis, high-fat eating can worsen impaired fat digestion and symptoms; only after recovery does the review see keto as a possible option, and clinical studies are still needed. Keto is also considered unsuitable in acute liver failure. For metabolic dysfunction-associated fatty liver disease (MAFLD), by contrast, the review considers keto a possible treatment option; that does not automatically apply to other chronic liver diseases. In familial hypercholesterolaemia the effect of keto has barely been studied. It can raise LDL cholesterol, and statin treatment may then need adjusting. The classification of propofol, an anaesthetic, rests mainly on one fatal case in a 10-year-old. A 2023 study of 65 patients and 165 anaesthesias found no propofol infusion syndrome, though isolated cases of acidosis, worsened seizures, and one case of rhabdomyolysis (muscle breakdown) did occur. Tell your anaesthetist about your diet before any procedure.
Kidney disease: the stage matters
In early stages (G1 to G3a, eGFR 45 or above), the review says keto is not necessarily ruled out. From G3b (eGFR below 45) the data are insufficient, and the kidneys handle ketones, acid loads, electrolytes, and fluid less well; the review treats this as a relative contraindication. Protein matters too: the KDIGO 2024 guideline suggests about 0.8 g of protein per kg of body weight per day in G3 to G5 and advises against more than 1.3 g/kg when the disease is at risk of progressing. The ADA Standards of Care 2026 currently do not recommend very-low-carbohydrate eating for people with kidney disease in general. A 2025 review in the Journal of Nephrology calls data in obesity and polycystic kidney disease promising but sees open safety questions, especially long term and with severely reduced kidney function.
SGLT2 inhibitors: the ketoacidosis warning
SGLT2 inhibitors such as empagliflozin (Jardiance) and dapagliflozin (Farxiga, Forxiga) are used for type 2 diabetes, heart failure, and chronic kidney disease. The US prescribing information for dapagliflozin (July 2026) explicitly names a ketogenic diet as a possible trigger of ketoacidosis, and the ADA Standards of Care 2026 advise avoiding very-low-carbohydrate eating on these drugs. The review also points to a US endocrinology society that suggests stopping the drug before starting keto; that decision belongs with your care team. The danger is that blood glucose may be only moderately raised in this kind of ketoacidosis. Ketoacidosis has also been reported, less often, in people without diabetes. Warning signs listed in the EU product information for empagliflozin are nausea, vomiting, loss of appetite, abdominal pain, excessive thirst, difficulty breathing, confusion, unusual fatigue, or sleepiness. If you suspect ketoacidosis, get medical help immediately, whatever your glucose reading, and do not take the drug again until a doctor tells you to. Without symptoms the opposite applies: do not stop the drug on your own, as it is often prescribed for heart failure or kidney disease as well. If you are planning keto, decide with your care team beforehand whether to drop keto or have the medication changed. If you also use insulin, say so explicitly: according to the EU product information, a sudden cut in insulin dose also raises the ketoacidosis risk on these drugs. The drug should also be paused for major surgery or serious acute illness in hospital, so raise both the drug and keto with your care team yourself. The authors of 2025 data from the telemedicine provider Virta Health weigh this differently: among people with type 2 diabetes on keto, the rate of diabetic ketoacidosis was 0.37 per 1,000 person-years in those never on an SGLT2 inhibitor and 2.90 in those who took one during treatment or were told to stop it before the diet change (unadjusted 7.18-fold, according to the authors). The authors, some of them company employees offered stock options, consider the risk possibly manageable with home ketone testing. Their patients, however, had medical supervision and followed a fixed safety protocol. These figures come from a single centre, and a meter alone does not replace that care.
Insulin, sulphonylureas, metformin, and GLP-1 drugs
Insulin and sulphonylureas are dosed for a higher carbohydrate intake. When intake falls sharply, hypoglycaemia is a risk if the dose stays the same; for type 2 diabetes, the review names a medically supervised dose reduction or stopping the drug as possible consequences. In type 1 diabetes hypoglycaemia is also a risk, but stopping is not an option: the body lacks its own insulin, so it must never be left out entirely. A specialist adjusts the dose. According to the review, diabetic ketoacidosis in this group appears sporadic but remains a known risk. The review explicitly does not place metformin among the drugs carrying this hypoglycaemia warning and does not call for routine dose adjustment; it describes a similar direction of effect. A change of diet should still be medically supervised, since the ADA notes that diabetes medications may need adjusting on very-low-carbohydrate plans. GLP-1 receptor agonists also act in the same direction: the review considers a lower dose probably possible and points out that hypoglycaemia can occur. For more, see GLP-1 vs. keto.
Blood pressure drugs, antiepileptics, lithium, and other medications
Keto can lower blood pressure, so people on antihypertensive drugs risk low blood pressure if the dose is not reviewed; the ADA also calls for blood pressure monitoring on very-low-carbohydrate plans. Diuretics may add to the water and electrolyte losses of the early phase. Antiepileptic drugs call for monitoring. Topiramate and zonisamide can promote metabolic acidosis alongside keto, so serum bicarbonate is checked; the authors of a paper cited in the review still see no need to avoid the combination with these two drugs. Levels of some drugs, including lamotrigine, carbamazepine, valproate, and clobazam, can fall on keto. The review recommends monitoring valproate levels, as a dose change may be needed. Only your neurology team should change the dose. Lithium has a narrow therapeutic window, and the kidneys clear it much like sodium, so its level can shift. The review recommends monitoring it before and during keto. Other notes concern corticosteroids, which can raise blood glucose, and highly fat-soluble drugs such as amiodarone, tacrolimus, methadone, and some antipsychotics. A high-fat diet may increase their absorption and with it the risk of side effects, so have the dose reviewed. The review stresses that its list is not exhaustive.
Pregnancy and breastfeeding
The ADA Standards of Care 2026 currently do not recommend very-low-carbohydrate eating during pregnancy or breastfeeding. The review says a well-formulated keto diet may be safe but relies on only a few case reports, and it requires extreme care and clinical supervision; pregnancy may be a poor time to start. An International League Against Epilepsy task force (2026) states that safety for mothers and babies is not yet known. In a 2018 US case-control study of 1,740 cases and 9,545 controls, women in the lowest 5% of carbohydrate intake before conception (not a pure keto group) were more likely to have a child with a neural tube defect, a malformation of the brain or spinal cord (adjusted odds ratio 1.30; 95% CI 1.02 to 1.67). They got less than half as much folic acid from food as other women. This is an association, not proof of cause, but it is a good reason to raise plans for pregnancy early. In a survey of women who followed keto while breastfeeding, one of 21 reported lactation ketoacidosis, a dangerous build-up of acid in the blood during breastfeeding; the review suggests other factors probably contributed, such as very low food intake.
Other groups that require extra caution
With gallstones, existing stones are more likely to move into the bile ducts on a high-fat diet and trigger biliary colic or complications such as pancreatitis. After gallbladder removal, keto is possible with care, though there are few studies; the review considers it sensible to increase fat gradually and spread it over three to four meals. People with an electrolyte deficiency or cardiac arrhythmias should have their levels checked first, because more sodium, potassium, and magnesium are lost during adaptation (see our guide to the keto flu). The ADA currently does not recommend very-low-carbohydrate eating for children; medical ketogenic therapies, such as for epilepsy, belong with specialist teams. For people who are underweight, the review suggests keto may not be the right approach because it suppresses appetite. Periods of intense stress and recovery from surgery are poor times to start. In intense training, adaptation is estimated to take at least four weeks, and keto is probably not optimal for high-intensity efforts, although the evidence is mixed. The ADA does not recommend very-low-carbohydrate eating for people with or at risk of disordered eating. The small anorexia case series cited in the review are preliminary and not a treatment recommendation; care belongs with specialists.
How to start keto safely if you are on medications
If you take any prescription medication, especially for diabetes, heart disease, epilepsy, mental health conditions, hypertension, or kidney disease, speak with your doctor before starting a ketogenic diet. Agree whether any doses should change from day one and which values to check and how often. Depending on your situation, that may mean blood glucose, ketones, kidney function, electrolytes, lipids, blood pressure, or drug levels. Dose adjustments may be needed quickly. Cutting carbohydrates abruptly is particularly risky for people who depend on insulin, because their insulin requirement can fall rapidly and hypoglycaemia can follow. Our guide on how to get into ketosis explains how nutritional ketosis in healthy people differs from ketoacidosis and how to measure ketones.
FAQ
Can I do keto if I take metformin?
Metformin alone does not rule out keto. The review explicitly excludes it from the drugs carrying a particular hypoglycaemia warning and does not call for routine dose adjustment. A change of diet should still be medically supervised, because keto lowers blood glucose further and diabetes medications may need adjusting. Do not change your metformin dose without medical advice. If you also take insulin, a sulphonylurea, or an SGLT2 inhibitor, their warnings apply.
Is keto dangerous if you have kidney disease?
From stage G3b (eGFR below 45), chronic kidney disease is a relative contraindication in the review, because the kidneys handle ketones, acid loads, and electrolytes less well and good data are lacking. In early stages keto is not necessarily ruled out, but the ADA Standards of Care 2026 currently do not recommend very-low-carbohydrate eating for people with kidney disease in general. The KDIGO 2024 guideline suggests about 0.8 g of protein per kg of body weight per day from G3. See a nephrologist before making a major dietary change.
Can keto cause ketoacidosis if I take an SGLT2 inhibitor?
Yes. The US prescribing information for dapagliflozin explicitly names a ketogenic diet as a possible trigger, and the ADA Standards of Care 2026 advise avoiding very-low-carbohydrate eating on SGLT2 inhibitors. In ketoacidosis, blood pH drops dangerously while blood glucose may be only moderately raised. For nausea, vomiting, abdominal pain, excessive thirst, difficulty breathing, confusion, or unusual fatigue, get medical help immediately, even if your glucose reading looks fine, and pause the drug until a doctor decides. Without such symptoms, do not stop the drug on your own; plan the approach with your care team before starting keto.
Can I do keto while pregnant or breastfeeding?
The ADA Standards of Care 2026 currently do not recommend very-low-carbohydrate eating during pregnancy or breastfeeding, and safety for mother and baby has not been established. Avoid starting keto during this time. Anyone who needs it for medical reasons, such as certain forms of epilepsy, should continue only under close medical supervision. If you are planning a pregnancy, raise it early, not least because of folic acid intake.
What should I watch for with blood pressure medication?
Keto can lower blood pressure, so your current dose may become too high. The review therefore points to a risk of low blood pressure. Measure regularly and ask your doctor to review the dose. With diuretics, the early phase adds further water and electrolyte losses. Change the dose only on medical advice.