TL;DR: A ketogenic diet lowers triglycerides by 20–40%, raises HDL by 10–20% and improves insulin resistance substantially. LDL is variable — in roughly 30% of users it rises markedly (LMHR phenomenon). Electrolytes need immediate attention; lipids should only be evaluated after 8–12 weeks.
This article does not replace medical advice. If you have pre-existing conditions, talk to a doctor before starting keto.
What Ketosis Does Inside the Body
A ketogenic diet means fewer than 50 g of carbohydrates per day, 70–80% of calories from fat, 15–25% from protein. After 2 to 4 days the glycogen stores are 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. Your blood panel after 12 weeks of keto looks different from the one before. Some changes are consistent and well-documented; others are variable and debated. This guide covers both.
Ketosis measurement: three methods compared
| Method | Accuracy | Convenience | Cost |
|---|---|---|---|
| Blood BHB (finger prick) | High | Medium | ~€1–2 per test |
| Urine strips | Medium (early), low (week 3+) | High | <€0.30 per strip |
| Breath ketone meter (KETONIX, etc.) | Medium | High | One-time ~€100–200 |
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 and not a target.
Blood Sugar and Insulin: the Clearest Changes
If you can track only one marker, choose fasting insulin. It drops reliably by 30 to 50% on keto — in people with insulin resistance often even more. Fasting blood glucose also falls, typically by 10 to 20 mg/dl.
HbA1c — the three-month blood sugar average — drops in type 2 diabetics on keto by an average of 1.0 to 1.5 percentage points (Hallberg et al. 2018). In non-diabetics the changes are smaller: typically 0.3 to 0.5 points, depending on baseline.
HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) improves substantially — the value often drops below 1.5, indicating well-controlled insulin sensitivity. HOMA-IR = fasting glucose (mmol/l) × fasting insulin (mIU/l) ÷ 22.5.
A concrete example: your fasting glucose is 105 mg/dl and fasting insulin 12 mIU/l. HOMA-IR = (5.8 × 12) ÷ 22.5 = 3.1 — clearly elevated. After 12 weeks of keto: glucose 90 mg/dl, insulin 7 mIU/l, HOMA-IR = (5.0 × 7) ÷ 22.5 = 1.6. In Lab2go you track this trend 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 drop in most keto users by 20 to 40%. This is one of the most consistent findings. High triglycerides are driven mainly by carbohydrates and sugar — remove that driver and the numbers follow. Target: below 150 mg/dl, optimal below 100 mg/dl.
HDL typically rises by 10 to 20%. This also improves the triglyceride/HDL ratio — an important 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. Anyone seeing LDL above 160 mg/dl should get ApoB measured (target below 90 mg/dl) and consider Lp(a) as well. More on interpreting cholesterol in the guide Understanding Cholesterol Values.
Timing is critical: do not test lipids during the adaptation phase (first 8 weeks). Body fat is being mobilised and values are skewed. Values are only meaningful after 8 to 12 weeks of stable keto.
| Biomarker | Typical change | 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 a normal metabolic shift: the liver is switching to fat metabolism. Values more than 3 times the upper limit (ALT above 135 U/L in men) warrant attention.
Long-term — after 12 weeks of stable keto — liver values in fatty liver patients often fall substantially. Keto is one of the most effective interventions for non-alcoholic fatty liver disease (NAFLD): liver weight, inflammation and fat content decrease.
To understand your baseline liver values, read 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.
Normal 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. Anyone with prior gout should monitor uric acid during the first 4 weeks.
Inflammation Markers and Immune Values
hs-CRP — high-sensitivity C-reactive protein — frequently drops on keto. Keto reduces insulin and thereby a key driver of systemic inflammation. Studies show reductions of 20 to 30% in people with elevated baseline values. Target: below 1 mg/l for lowest cardiovascular risk.
Interleukin-6 (IL-6) and TNF-α also improve in keto studies, particularly in overweight individuals. These markers are not part of a standard panel but are relevant for deeper monitoring. 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, you lose potassium and magnesium too. This is the primary cause of the keto flu.
Sodium: loss of 1 to 2 g daily in the first week. Supplement with 2 to 3 g extra sodium (broth, sea salt). Blood sodium levels usually stay within normal range as the body compensates — the subjective deficit shows up as fatigue and headaches.
Potassium: daily requirement rises to 3.5 g. Keto-friendly sources: avocado (roughly 700 mg per 100 g), salmon, pumpkin, nuts. If you experience cramps or palpitations, check potassium levels (normal range: 3.5–5.0 mmol/l).
Magnesium: supplement 300 to 500 mg daily — glycinate or malate preferred for tolerability. Magnesium deficiency shows up as muscle cramps, sleep issues and irritability. More in the guide on supplement basics.
| Electrolyte | Problem on keto | Solution |
|---|---|---|
| Sodium | Loss → fatigue, headaches | +2–3 g/day (broth, salt) |
| Potassium | Increased demand | 3.5 g/day from food + supplement if needed |
| Magnesium | Loss + often already low | 300–500 mg glycinate daily |
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 as an adaptation to lower carbohydrate intake.
Testosterone (men): usually stable on moderate keto. Very calorie-restricted or protein-restricted keto can lower testosterone — Volek et al. (2005) described this effect with extreme low-carb. Adequate protein (1.6–2.0 g/kg body weight) and sufficient calories are 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 (optimal: below 4:1). Olive oil, salmon and walnuts improve it. Supplement: 2 to 4 g EPA/DHA daily. See also the guide on intermittent fasting and biomarkers for further context.
Keto Variants and Their Effect on Blood Values
Not all keto protocols are equal.
Standard Keto (SKD): classic, below 50 g carbohydrates daily. Strongest ketosis, greatest triglyceride reduction — but problematic for LDL hyper-responders when saturated fats dominate.
Targeted Keto (TKD): carbohydrates around training only. A good option for strength athletes; softens 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 better 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.
Who Benefits and Who Should Be Cautious
Clear benefit groups (well-evidenced):
- Type 2 diabetes and insulin resistance (strongest data, Hallberg 2018)
- Non-alcoholic fatty liver disease (NAFLD)
- Epilepsy (established for decades)
- Obesity with insulin resistance
Potential benefit groups (data available, not conclusive):
- Neurodegeneration (Alzheimer, Parkinson — early study data)
- Certain cancers as adjunct therapy
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
Monitoring Protocol for Keto Beginners
Keto without blood tests is biohacking in the dark. This protocol gives you structure.
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.
Week 4: Electrolytes (sodium, potassium, magnesium), uric acid, blood BHB (self-testing daily recommended).
Week 12 — first full check: Repeat all baseline values. Only now are lipid values meaningful. If LDL is above 160 mg/dl: measure ApoB, consider Mediterranean keto, consider a lipid specialist.
Annually: Full biomarker check. Add body composition measurement (DEXA or bioimpedance).
If LDL rises: ApoB, Lp(a), CAC score (coronary artery calcium score) worth considering. Discuss with a cardiologist.
In Lab2go you track BHB daily, monitor biomarker trends over months and correlate lab values with weight loss and how you feel. Check the pricing plans to find the right package for your monitoring level.
For the big picture — all biomarkers in context — read the guide on understanding blood values.
Conclusion: Keto and Blood Values, Realistically
Keto changes blood values in measurable and reproducible ways. For insulin resistance, triglycerides and HDL it is one of the most effective dietary interventions available. Liver values, inflammation markers and blood sugar also show clear improvements.
LDL is the exception — variable, contested and problematically elevated in some users. The LMHR phenomenon is real, but its long-term clinical significance is not yet resolved. Anyone who sees LDL rising should measure ApoB and not continue without reassessment.
Three steps to get started:
- Set a baseline. Full blood panel before starting keto, including ApoB and fasting insulin.
- Address electrolytes immediately. Sodium, potassium and magnesium from day one.
- Evaluate lipids only after week 12. Do not test during the adaptation phase.
For a broader introduction to biomarker tracking and supplementation, read the supplement beginners guide and the guide on intermittent fasting and biomarkers.
This article does not replace medical advice. With pre-existing conditions — especially kidney, gallbladder or thyroid — consult a doctor before starting keto.
Article FAQ
- When should I test lipids on keto?
- Not in the first 8 weeks. During the adaptation phase lipid values are often distorted — stored body fat is being mobilised and triglycerides fluctuate. Wait 8 to 12 weeks after starting, then the values reflect your stable keto metabolism. Test fasting (12–14 hours) and without intense training in the previous 48 hours.
- Why does LDL rise sharply in some people on keto?
- Around 30% of keto users show a marked LDL increase — a phenomenon described by Dave Feldman as the Lean Mass Hyper-Responder (LMHR). It tends to affect lean, athletic individuals with low triglycerides and high HDL. The clinical significance remains unclear. Anyone seeing LDL above 160 mg/dl should also measure ApoB and Lp(a).
- 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 electrolyte loss — sodium, potassium and magnesium are excreted at a higher rate because falling insulin reduces the kidney's sodium reabsorption. Symptoms clear within 3 to 7 days. Prevention: 2–3 g extra sodium daily, 3.5 g potassium, 300–500 mg magnesium glycinate.
- 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. Anyone with prior gout should check uric acid every 4 weeks.
- Does keto affect thyroid values?
- Free T3 (fT3) can drop by 10 to 20% on keto. This is not a sign of thyroid disease as long as TSH stays stable and no symptoms appear. The body reduces peripheral T3 conversion as an adaptation to lower carbohydrate intake. Check TSH and fT3 after 12 weeks to confirm.
- Which keto variant is easiest on lipids?
- 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. If you have LDL concerns, replace saturated fats with monounsaturated ones.
- How do I measure my ketone level most accurately?
- Blood BHB (β-hydroxybutyrate) is 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 (e.g. KETONIX) are convenient but less precise than blood readings. Measure fasting in the morning for peak levels, midday for a daily average.
- Does everyone benefit equally from keto?
- No. The strongest evidence is for type 2 diabetes and insulin resistance (Hallberg et al. 2018) and non-alcoholic fatty liver disease. Keto has been an established epilepsy treatment for decades. In healthy, normal-weight individuals the blood value improvements are smaller. Endurance and power athletes in anaerobic sports often experience a performance drop.
- Do I need supplements on keto?
- For a well-planned keto diet three supplements stand out: magnesium (300–500 mg glycinate daily for cramps and sleep), sodium (2–3 g extra daily) and potassium (from avocado, salmon, nuts or 1 g supplement if needed). Very restrictive keto without vegetables can deplete vitamin C. Omega-3 (2–4 g EPA/DHA daily) is worthwhile when fat sources are one-sided.
- How long until blood values stabilise on keto?
- Triglycerides often drop 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.
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