TL;DR: Studies often report lower triglycerides and insulin and higher HDL on a ketogenic diet. LDL behaves inconsistently — in roughly 30% of users a marked rise is described (LMHR phenomenon). Electrolytes shift early; lipid values are hard to interpret in the first 8–12 weeks.
This article is for information only and does not replace medical advice. A change of diet, taking any supplement, the dose a doctor has prescribed and any treatment belong in a doctor’s hands — especially with pre-existing conditions.
What Ketosis Does Inside the Body
A ketogenic diet means very low carbohydrate intake (often defined as under about 50 g of carbohydrates each day), with 70–80% of calories from fat and 15–25% from protein. After 2 to 4 days the glycogen stores are usually empty. The liver starts converting fatty acids into β-hydroxybutyrate (BHB), acetoacetate and acetone — the ketone bodies that now replace glucose as the primary fuel.
This metabolic shift is measurable. A blood panel after 12 weeks of a ketogenic diet can look different from the one before. Some changes are consistent and well-documented in studies; others are variable and debated. This article covers both, for information only.
Ketosis measurement: three methods compared
| Method | Accuracy | Convenience |
|---|---|---|
| Blood BHB (finger prick) | High | Medium |
| Urine strips | Medium (early), low (week 3+) | High |
| Breath ketone meter | Medium | High |
Blood BHB fasting in the morning: 0.5–1.5 mmol/l = light ketosis, 1.5–3.0 = moderate, 3.0–5.0 = deep ketosis. Values above 5 mmol/l in healthy adults without diabetes are rare.
Blood Sugar and Insulin: the Clearest Changes
Fasting insulin is among the markers that change most clearly in studies. Reductions of 30 to 50% are reported — in people with insulin resistance sometimes more. Fasting blood glucose also falls in studies, typically by 10 to 20 mg/dl.
HbA1c — the three-month blood sugar average — fell by an average of 1.0 to 1.5 percentage points in studies of type 2 diabetes on a ketogenic diet (Hallberg et al. 2018). In non-diabetics the changes are smaller: typically 0.3 to 0.5 points, depending on baseline. Anyone taking diabetes medication discusses dietary changes with a doctor.
HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) often improves in studies — values below 1.5 are considered well-controlled insulin sensitivity. HOMA-IR = fasting glucose (mmol/l) × fasting insulin (mIU/l) ÷ 22.5.
A worked example with fictional values: fasting glucose 105 mg/dl and fasting insulin 12 mIU/l. HOMA-IR = (5.8 × 12) ÷ 22.5 = 3.1 — clearly elevated. A later reading of glucose 90 mg/dl and insulin 7 mIU/l would give HOMA-IR = (5.0 × 7) ÷ 22.5 = 1.6. In Lab2go you track trends like this over months.
For deeper context on insulin resistance diagnostics, read the guide on insulin resistance and HOMA-IR.
Lipids: More Complex Than the Headlines Suggest
Keto has a mixed reputation with lipids. The reality is more nuanced than “keto raises cholesterol.”
Triglycerides dropped by 20 to 40% in most keto users in studies. This is among the more consistent findings. High triglycerides are linked, among other things, to carbohydrate and sugar intake — remove that factor and the numbers tend to follow. Reference range: below 150 mg/dl, optimal below 100 mg/dl.
HDL typically rises by 10 to 20%. This also affects the triglyceride/HDL ratio — a risk marker that is considered favourable below 2.
LDL is the contested point. In roughly 30 to 40% of users LDL rises, sometimes substantially. The effect is most pronounced in lean, athletic individuals with low triglycerides — a phenomenon Dave Feldman calls the Lean Mass Hyper-Responder (LMHR). The underlying hypothesis: lean people with high energy demands mobilise more VLDL, raising LDL particle count. The long-term cardiovascular significance of this pattern has not yet been definitively established by the scientific literature.
ApoB — the protein on atherogenic lipoproteins — is clinically more relevant than LDL cholesterol alone. When LDL rises, ApoB usually does too. With LDL above 160 mg/dl, ApoB (reference: below 90 mg/dl) and Lp(a) are often measured as well; whether that makes sense is for the treating doctor to decide. More on interpreting cholesterol in the guide Understanding Cholesterol Values.
Timing: during the adaptation phase (first 8 weeks) lipid values are often distorted because body fat is being mobilised. They are usually meaningful only after 8 to 12 weeks of stable ketogenic eating.
| Biomarker | Change reported in studies | Timeframe |
|---|---|---|
| Triglycerides | −20 to −40% | 4–8 weeks |
| HDL | +10 to +20% | 8–16 weeks |
| LDL | variable: −10% to +50% | from week 8 |
| ApoB | mostly parallel to LDL | from week 8 |
Liver Values: Up First, Then Down
In the first 2 to 4 weeks ALT can rise slightly — 10 to 30% above baseline. This is regarded as a metabolic shift: the liver is switching to fat metabolism. Values more than 3 times the upper limit (ALT above 135 U/L in men) are followed up medically.
Long-term, studies in non-alcoholic fatty liver disease (NAFLD) have reported falling liver values and lower liver fat content after 12 weeks of a ketogenic diet. The evidence is limited, and results do not apply to everyone.
To put baseline liver values in context, see the guide on liver values explained.
Uric Acid: the Underestimated Risk in Weeks 1–4
Uric acid rises in almost everyone in the first weeks. The mechanism: ketone bodies and urate compete for the same renal transporter (OAT4). Ketones displace urate — excretion drops and blood levels rise.
Reference ranges: men below 7.0 mg/dl, women below 6.0 mg/dl. In weeks 2 to 4 on keto, values of 8 to 10 mg/dl are observed. In people without prior gout this usually causes no symptoms. In those with a gout history, it can trigger an attack — a real risk that is frequently underestimated.
After the adaptation phase (from week 6 to 8) uric acid normalises for most users. With known gout it is often monitored more closely during the first 4 weeks; this needs to be clarified with a doctor.
Inflammation Markers and Immune Values
hs-CRP — high-sensitivity C-reactive protein — frequently drops on keto. Insulin typically falls on keto, and with it a possible driver of systemic inflammation. Studies report reductions of 20 to 30% in people with elevated baseline values. Reference: below 1 mg/l corresponds to the lowest cardiovascular risk.
Interleukin-6 (IL-6) and TNF-α also show lower values in keto studies, particularly in overweight individuals. These markers are not part of a standard panel but are relevant for more detailed investigations. Details in the article on inflammation markers in blood.
Electrolytes: the First Week Determines Everything
When insulin drops, the kidneys excrete more sodium. With it, potassium and magnesium are lost too. This is regarded as the primary cause of the keto flu.
Sodium: the loss can be considerable in the first week. Blood sodium levels usually stay within the normal range as the body compensates — a deficit shows up more as fatigue and headaches.
Potassium: requirements can rise. Foods containing potassium include avocado, salmon, pumpkin and nuts. With cramps or palpitations a blood potassium level is informative (reference range: 3.5–5.0 mmol/l) — this needs to be clarified with a doctor.
Magnesium: a deficiency can show up as muscle cramps, sleep issues and irritability. Whether supplements come into question and what amount a doctor would set depends on lab values, kidney function and medication. Background in the supplement beginners guide.
| Electrolyte | What can change on keto | Possible signs |
|---|---|---|
| Sodium | Increased excretion | Fatigue, headaches |
| Potassium | Requirements and losses can rise | Cramps, palpitations |
| Magnesium | Loss, often already low beforehand | Cramps, sleep issues, irritability |
Whether and how electrolytes should be balanced needs to be clarified with a doctor.
Thyroid, Testosterone and Other Hormones
Free T3 (fT3) often drops by 10 to 20% on keto. This is not thyroid disease as long as TSH stays stable and no symptoms appear (cold intolerance, severe fatigue). The body reduces peripheral T3 conversion, described as an adaptation to lower carbohydrate intake.
Testosterone (men): usually stable on moderate keto. Very calorie-restricted or protein-restricted keto can lower testosterone; adequate protein and calorie intake is considered protective.
Vitamin D, B12 and ferritin: in a well-planned keto diet that includes meat, fish, eggs and avocado, these values typically stay stable. Exception: very restrictive keto without vegetables can limit vitamin C and folate.
Omega-6/Omega-3 ratio: critical on keto if fat sources are poor choices. Sausage, sunflower oil and soy oil are high in omega-6 — heavy consumption worsens the ratio (favourable: below 4:1). Olive oil, salmon and walnuts improve it. Whether omega-3 supplements come into question is clarified with a doctor. See also the guide on intermittent fasting and biomarkers for further context.
Keto Variants and Their Effect on Blood Values
Not all ketogenic eating patterns are equal.
Standard Keto (SKD): classic, very low in carbohydrates. Strongest ketosis, largest triglyceride drop — but problematic for LDL hyper-responders when saturated fats dominate.
Targeted Keto (TKD): carbohydrates around training only. Discussed mainly for strength athletes; may soften the fT3 decline.
Cyclical Keto (CKD): 5 days keto, 2 days high-carb. Can blunt LDL rises and stabilise thyroid values. Complex in practice.
High-Protein Keto: protein above 30% of calories. Gluconeogenesis from protein can weaken ketosis — not ideal for deep ketosis, but more favourable than standard keto when LDL is a concern.
Mediterranean Keto: olive oil, fish, nuts and avocado as primary fat sources. Best lipid profile outcomes in studies; more LDL-friendly than butter-based standard keto.
Evidence by Group and Cautions
Groups with the best evidence:
- Type 2 diabetes and insulin resistance (strongest data, Hallberg 2018)
- Non-alcoholic fatty liver disease (NAFLD)
- Epilepsy (used under medical supervision for decades)
- Obesity with insulin resistance
Groups with preliminary evidence (not conclusive):
- Neurodegeneration (Alzheimer, Parkinson — early study data)
- Certain cancers (early study data, no established conclusions)
Caution advised for:
- Tendency toward kidney stones (increased oxalate formation)
- Gallstones or gallbladder conditions (higher fat load)
- Menstrual irregularities at very low carbohydrate intake
- Anaerobic athletes (sprinting, weightlifting)
- Pregnancy and breastfeeding
Long-term questions (not yet resolved):
- Nutrient deficiencies in poorly planned keto (fibre, folate, vitamin C)
- Microbiome changes (reduction of fibre-loving bacteria)
- LMHR with sharply elevated LDL — long-term cardiovascular risk unclear
Lab Values Over Time
Anyone who has a ketogenic diet medically supervised usually gets a sequence of lab checks. The overview below describes which values are typically looked at. The scope and timing are set by the treating doctor.
Before starting — baseline: Lipid panel including ApoB, HbA1c, fasting insulin, HOMA-IR, liver values (ALT, AST, GGT), kidney values (creatinine, uric acid), thyroid (TSH, fT3), hs-CRP, ferritin, vitamin D.
Around week 4: Electrolytes (sodium, potassium, magnesium), uric acid, blood BHB (as self-measurement).
Around week 12 — first full check: Repeat of the baseline values. Only now are lipid values readily interpretable. With LDL above 160 mg/dl, ApoB is often measured, the eating pattern discussed and, where appropriate, a lipid specialist consulted.
Annually: Full biomarker check. Body composition measurement (DEXA or bioimpedance) can be added.
If LDL rises: ApoB, Lp(a) and the CAC score (coronary artery calcium score) are discussed. A conversation with a cardiologist is common.
In Lab2go you record BHB values and biomarker trends over months; you compare them yourself with weight changes and how you feel. Check the pricing plans to find the right package for your tracking level.
For the big picture — all biomarkers in context — read the guide on understanding blood values.
Conclusion: Keto and Blood Values, Realistically
On a ketogenic diet, studies report measurable changes in blood values. They are most consistent for insulin, triglycerides and HDL. Changes in liver values, inflammation markers and blood sugar are also reported — with partly limited evidence.
LDL is the exception — variable, contested and markedly elevated in some users. The LMHR phenomenon is described, but its long-term clinical significance is not yet resolved. When LDL rises, ApoB is often measured as well; the next steps are for the doctor to decide.
Three points for context:
- Baseline. A full blood panel before starting, including ApoB and fasting insulin, provides reference values.
- Electrolytes. They shift early; whether and how they are balanced needs to be clarified with a doctor.
- Lipids. They are usually only readily interpretable after week 12, not during the adaptation phase.
For a broader introduction to biomarker tracking and background on supplements, read the supplement beginners guide and the guide on intermittent fasting and biomarkers.
This article is for information only and does not replace medical advice. With pre-existing conditions — especially kidney, gallbladder or thyroid — a change of diet, taking any supplement and any treatment belong in a doctor’s hands.
Article FAQ
- When are lipid values meaningful on a ketogenic diet?
- Usually not in the first 8 weeks. During the adaptation phase lipid values are often distorted — stored body fat is being mobilised and triglycerides fluctuate. After 8 to 12 weeks the values tend to reflect the stable keto metabolism better. Blood draws are usually taken fasting (12–14 hours) and without intense training in the previous 48 hours. The timing and scope of checks are set by the treating doctor.
- Why does LDL rise sharply in some people on keto?
- In around 30% of keto users a marked LDL increase is described — a phenomenon known as the Lean Mass Hyper-Responder (LMHR), described by Dave Feldman. It tends to affect lean, athletic individuals with low triglycerides and high HDL. The clinical significance remains unclear. With LDL above 160 mg/dl, ApoB and Lp(a) are often measured as well; whether that is needed is for the doctor to decide.
- What is the keto flu and how long does it last?
- Keto flu refers to symptoms in the first week: fatigue, headaches, irritability, muscle cramps. The cause is thought to be electrolyte loss — sodium, potassium and magnesium are excreted at a higher rate because falling insulin reduces the kidney's sodium reabsorption. Symptoms usually clear within 3 to 7 days. Whether and how electrolytes should be balanced needs to be clarified with a doctor, especially with pre-existing conditions or medication.
- Can keto trigger gout?
- In the first 2 to 4 weeks uric acid rises because ketone bodies and urate compete for the same renal transporter (OAT4) — ketones take priority, so urate excretion drops. In people with a history of gout this can trigger an attack. After the adaptation phase uric acid normalises for most people. With known gout, uric acid is often checked more closely during this period; this needs to be clarified with a doctor.
- Does keto affect thyroid values?
- Free T3 (fT3) can drop by 10 to 20% on keto. On its own this is not a sign of thyroid disease as long as TSH stays stable and no symptoms appear. The body is described as reducing peripheral T3 conversion in response to lower carbohydrate intake. TSH and fT3 are interpreted by a doctor over time, often after about 12 weeks.
- Which keto variant looks more favourable for lipids in studies?
- Mediterranean keto — using olive oil, fish, nuts and avocado as primary fat sources — shows the most favourable LDL and ApoB outcomes in studies. Standard keto with high saturated fat from butter, sausage and bacon raises LDL more in hyper-responders. Whether a different choice of fats makes sense when LDL is raised is discussed with a doctor or a dietitian.
- How can ketone levels be measured most accurately?
- Blood BHB (β-hydroxybutyrate) is considered the gold standard. Light ketosis: 0.5–1.5 mmol/l, moderate: 1.5–3.0 mmol/l, deep: 3.0–5.0 mmol/l. Urine strips become inaccurate after 2 to 3 weeks as the body uses ketones more efficiently. Breath ketone meters are convenient but less precise than blood readings. Readings taken fasting in the morning and at midday can differ considerably.
- For whom is the evidence on keto strongest?
- The strongest evidence is for type 2 diabetes and insulin resistance (Hallberg et al. 2018); data on non-alcoholic fatty liver disease are comparatively good as well. For epilepsy, a ketogenic diet has been used under medical supervision for decades. In healthy, normal-weight individuals the changes in blood values are smaller. Athletes in anaerobic sports (weightlifting, sprinting) often report a performance drop.
- What role do electrolytes and nutrients play on a ketogenic diet?
- On keto, sodium, potassium and magnesium shift early. A very restrictive diet without vegetables can also limit vitamin C intake, and one-sided fat choices shift the omega-6/omega-3 ratio. Whether supplements come into question, and what amount a doctor would set, depends on lab values, pre-existing conditions and medication. This article gives no recommendation to take anything.
- How long until blood values stabilise on keto?
- In studies triglycerides often dropped within 4 to 6 weeks. HDL rises more slowly, typically over 3 to 6 months. HbA1c needs at least 12 weeks because it reflects the 3-month average blood sugar. LDL fluctuates during the adaptation phase and stabilises after 8 to 12 weeks. Electrolyte shifts are felt within the first week.
This article is for general information only and is not a substitute for individual medical advice, diagnosis, or treatment. Discuss any changes to your diet, supplementation, or medication with a qualified healthcare professional.
Maritta Schmid, Heilpraktikerin (licence under the German Heilpraktikergesetz; non-medical health practitioner), Licence under the German Heilpraktikergesetz, issued by Gesundheitsamt Heilbronn (February 2010), Supervisory authority: Landratsamt Ostalbkreis – Gesundheitsamt Aalen
Heilpraktikerin & Founder
Schwäbisch Gmünd, Germany
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