If you follow a keto diet, the supplement that matters most isn’t a ketone product. It’s electrolytes: sodium, potassium and magnesium, ideally mostly from food, with a supplement to fill any gaps.
MCT oil and BHB salts come a distant second. MCT oil raises blood ketones modestly and may have a small effect on weight. BHB salts raise ketones only briefly, and drinking ketones isn’t the same as burning your own body fat.
This guide covers how much of each electrolyte the NIH recommends, what to check on labels, honest evidence grades for MCT oil and BHB salts, a sample day, and who shouldn’t try keto without medical supervision.
Why electrolytes come first
Many people feel rough in the first days or weeks of keto. A 2026 review of the diet’s side effects lists transient “keto flu” symptoms such as fatigue, headache and nausea among the most commonly reported problems, along with digestive upset and frequent urination.
The usual explanation is that cutting carbs makes your body shed water, and minerals go with it. It’s a plausible idea that hasn’t been tested much in formal trials, but replacing sodium, potassium and magnesium is cheap and low-risk for most healthy adults.
A whole-food keto diet also cuts out many packaged and prepared foods, which the FDA says supply over 70% of the sodium Americans eat. So your sodium intake can drop sharply without you noticing.
Sodium: salt your food, within reason
The Dietary Guidelines for Americans advise adults to keep sodium below 2,300 mg a day, which the FDA notes is about one teaspoon of table salt. The average American eats about 3,400 mg.
There is no official keto-specific sodium target. Keto guides commonly suggest salting food to taste, sipping broth or using an electrolyte drink in the first few weeks, especially if you feel headachy or lightheaded. That’s a reasonable approach for healthy adults, but it isn’t a reason to go far above typical intakes.
If you have high blood pressure, heart failure or kidney disease, or take blood pressure medication or diuretics, don’t add salt without talking to your doctor.
Potassium: get it from food first
The NIH Office of Dietary Supplements (ODS) sets an Adequate Intake of 3,400 mg a day for men and 2,600 mg for women. Many of the richest sources on its list, such as dried apricots, lentils, potatoes and beans, are high in carbs, so keto eaters need to lean on lower-carb options.
| Keto-friendly food | Serving | Potassium |
|---|---|---|
| Spinach, raw | 2 cups | 334 mg |
| Chicken breast, grilled | 3 oz | 332 mg |
| Salmon, Atlantic, farmed, cooked | 3 oz | 326 mg |
| Beef top sirloin, grilled | 3 oz | 315 mg |
| Tomato, raw | 1 medium | 292 mg |
| Broccoli, cooked | ½ cup | 229 mg |
| Asparagus, cooked | ½ cup | 202 mg |
Values are from the NIH ODS potassium fact sheet.
Don’t expect much from potassium pills. The ODS notes that most potassium-only supplements contain up to 99 mg, about 2% of the Daily Value, partly because the FDA has linked some potassium chloride drugs above that amount to small-bowel injury.
Salt substitutes (“lite” salts) replace some sodium with potassium chloride and can contain roughly 440–2,800 mg of potassium per teaspoon. Use them sparingly: the ODS warns that very large amounts of potassium from supplements or salt substitutes can exceed what even healthy kidneys can clear.
Magnesium: useful, but mind the upper limit
The RDA for adults is 400–420 mg a day for men and 310–320 mg for women. Low-carb foods help: according to the ODS, pumpkin seeds provide 156 mg per ounce, chia seeds 111 mg per ounce, almonds 80 mg per ounce and boiled spinach 78 mg per half cup.
If you add a supplement, keep it at or below 350 mg a day from supplements, the upper limit for adults. Higher doses often cause diarrhea, sometimes with nausea and cramping, and very large doses can be dangerous.
Which form?
The ODS says the aspartate, citrate, lactate and chloride forms tend to be absorbed better than magnesium oxide and sulfate. Glycinate is popular too, though the fact sheet doesn’t rank it. Whatever you choose, check the label for the amount of elemental magnesium per serving.
Talk to your doctor first if you have kidney disease, because the risk of magnesium toxicity rises when the kidneys can’t clear it. Magnesium can also interfere with osteoporosis drugs called bisphosphonates and with tetracycline and quinolone antibiotics, so ask your pharmacist how to space doses.
| Mineral | Adult reference intake | Keto-friendly sources | Supplement notes |
|---|---|---|---|
| Sodium | Below 2,300 mg a day (general guidance) | Salted food, broth | No keto-specific target; ask a doctor if you have high blood pressure, heart or kidney disease |
| Potassium | 3,400 mg (men), 2,600 mg (women) | Leafy greens, salmon, chicken, beef, tomatoes, broccoli | Pills usually 99 mg or less; caution with kidney disease and some blood pressure drugs |
| Magnesium | 400–420 mg (men), 310–320 mg (women) | Pumpkin seeds, chia, almonds, spinach | Supplements no more than 350 mg a day; citrate, chloride, lactate and aspartate absorb better than oxide |
How to choose an electrolyte product
A ready-made electrolyte powder is the simplest way to cover a gap on days you feel off or sweat a lot. Labels vary widely, so check these points:
- Sugar and carbs per serving: zero or close to it.
- Sodium in milligrams: enough to matter, and counted toward your daily total.
- Potassium: often modest, so food should still do most of the work.
- Magnesium amount and form: keep all supplemental magnesium within 350 mg a day.
- No proprietary blends, and ideally a third-party seal such as NSF Certified for Sport or Informed-Choice.
Formulas change, so read the current label before you buy.
MCT oil: optional, with modest evidence
MCT oil is made of medium-chain triglycerides, mainly caprylic acid (C8) and capric acid (C10). Coconut oil contains only small amounts of these; in the study below, it was about 3% C8 and 5% C10.
In a small crossover study, 9 healthy adults took two 20 mL doses of different test oils on separate days. Pure C8 raised blood ketones the most, and coconut oil’s ketone peak was only about a quarter of C8’s.
For weight, a 2015 meta-analysis of 13 randomized trials (749 people) found that replacing long-chain fats with MCTs led to about 0.5 kg (1.1 lb) more weight loss on average, with small reductions in waist size and body fat. The authors noted that many trials lacked quality details and that commercial bias was detected.
How to use it
- Start with about 1 teaspoon a day and increase slowly, because larger amounts can upset your stomach.
- It is pure fat, so its calories count toward your daily total.
- Check the label for C8 and C10 content; C8 had the biggest ketone effect in the study above.
- MCT powders contain added ingredients, so check carbs per serving.
BHB salts: the weakest case
BHB salts are beta-hydroxybutyrate, one of the ketones your liver makes, bound to minerals such as sodium, potassium, calcium or magnesium. They’re marketed as a shortcut to ketosis.
A 2017 University of Oxford study measured what happens when people drink them. In 15 healthy adults, ketone salt drinks raised blood D-BHB to a peak of about 1.0 mmol/L, compared with 2.8 mmol/L for a ketone ester drink, and levels returned to baseline within 3–4 hours. About half the BHB in the salts was the L-form, which stayed in the blood for over 8 hours.
Two things follow. The effect is short-lived, and raising blood ketones with a drink isn’t the same as burning more of your own body fat, because those ketones came from the drink. The study measured blood ketones, not fat loss.
BHB salts also carry a mineral load. A serving can add a meaningful amount of sodium or other minerals, so count it toward your daily totals and skip it if you’ve been told to limit sodium. If you’re curious, treat BHB salts as an optional extra and check the label for BHB and each mineral per serving.
Evidence grades at a glance
| Supplement | What it does | Evidence | Priority | Main caution |
|---|---|---|---|---|
| Electrolytes (sodium, potassium, magnesium) | Replace minerals; may ease early keto symptoms | Nutrient needs well established; few keto-specific trials | First | Kidney disease, heart and blood pressure conditions, some medications |
| MCT oil | Raises blood ketones; possibly a small weight effect | Moderate for ketones (small studies); modest for weight (about 0.5 kg) | Optional | Stomach upset; extra calories |
| BHB salts | Brief rise in blood ketones (3–4 hours) | Weak; the key study measured ketones, not fat loss | Lowest | Mineral load, especially sodium |
| “Keto diet pills” promising weight loss | Marketing claims | Not supported | Skip | Check for stimulants and proprietary blends |
Like any diet, keto leads to fat loss only if it helps you eat less overall; our guide to how a calorie deficit works explains why. If a pill promises keto results without the diet, read our guide to how fat burners actually work before buying.
A sample keto supplement day
- Breakfast: Eggs scrambled with 2 cups of spinach, salted to taste. Coffee or tea.
- Lunch: Salmon salad with tomato, olive oil and pumpkin seeds. If you use MCT oil, add a teaspoon to the dressing.
- Afternoon: A mug of broth or one serving of a sugar-free electrolyte drink, especially on training days or if you feel headachy.
- Dinner: Grilled chicken or steak with broccoli and asparagus.
- Evening: A magnesium supplement only if your food intake is low, staying within 350 mg from supplements.
Using the values in the potassium table, the spinach, salmon, tomato, chicken, broccoli and asparagus alone supply about 1,700 mg of potassium, roughly half to two-thirds of the Adequate Intake before counting anything else. Keep protein at your usual target too; see how much protein you need to lose weight. BHB salts aren’t needed.
Who should not do keto without medical supervision
Keto isn’t for everyone. A 2026 review of the diet’s contraindications and drug interactions highlights several groups who need medical guidance before cutting carbs this far:
- People taking SGLT2 inhibitors, such as empagliflozin, dapagliflozin or canagliflozin. Combining them with keto has been linked to euglycemic diabetic ketoacidosis, a dangerous buildup of acid in the blood that can happen with near-normal blood sugar. In a review of 14 such cases, over 90% of patients were hospitalized within four weeks of starting the diet.
- People using insulin or sulfonylureas. Low blood sugar is a reported risk, so doses may need adjusting under supervision.
- Anyone who is pregnant or breastfeeding.
- People with kidney or liver disease, pancreatitis, gallbladder disease or no gallbladder.
- People with familial hypercholesterolemia, heart rhythm problems or medication-treated high blood pressure.
- Anyone who is underweight.
- People with rare inherited disorders of fat metabolism or porphyria.
The review also flags interactions with metformin, GLP-1 receptor agonists such as semaglutide, diuretics, anti-seizure drugs and corticosteroids, so anyone taking these should plan keto with their doctor.
We would add anyone under 18 or with a history of disordered eating. If you take an SGLT2 inhibitor, MedlinePlus’s empagliflozin page lists nausea, vomiting, stomach-area pain, tiredness and difficulty breathing as signs of ketoacidosis to act on, even when blood sugar is below 250 mg/dL.
