Your potassium is 5.8 mmol/L: above the lab's threshold. A licensed medical professional calls and says "go to the ER." But you feel fine, and you know you did a hard workout yesterday. Is this a real emergency or a pre-analytical error?
Every athlete who tracks blood work regularly eventually encounters an abnormal result that does not make sense. You feel fine, your training is going well, and the result contradicts everything you know about your health. In many cases, the result is correct and needs attention. But in a meaningful share of cases, the abnormality is caused by how the blood was drawn, handled, or processed, not by an actual health problem.
A classic scenario: you are 8 weeks into a cycle, your estrogen is controlled, your blood pressure is fine, and you feel strong. Then your eGFR comes back at 58 mL/min/1.73 m². The reference range starts at 60. You panic, think about kidney damage, and start planning a PCT. But eGFR is calculated from creatinine, and creatinine is directly affected by muscle mass, recent training, and creatine supplementation. A single eGFR of 58 in a muscular athlete who trained legs 48 hours prior is not a signal of renal failure. It is a signal that the equation used to estimate GFR was never validated for people with your body composition. Redraw fasted, rested, and hydrated. If it still reads below 60, then you start investigating.
Learning to distinguish lab error from real signal is one of the most valuable skills you can develop as someone who regularly tests blood. Here is how to tell the difference.
Pre-analytical errors happen before the sample is analyzed. They occur during collection, handling, transport, or storage. In athletes, three specific errors account for the majority of false abnormal results:
Hemolysis: The Athlete's #1 Lab Error
Hemolysis occurs when red blood cells rupture during the draw, releasing their contents into the plasma. This is more common in athletes because muscular arms have deeper, more resilient veins that are harder to puncture cleanly. The phlebotomist may need to "dig" to find the vein, causing mechanical damage to red cells as they pass through a narrow or partially occluded needle.
You can often catch hemolysis before the lab does. When the phlebotomist draws blood, look at the tube. If the plasma or serum appears pink or red instead of clear yellow, that is hemolysis. Some labs automatically flag the sample, but not all do. If you see a pink tinge, ask for a redraw on the spot. Also, ask the phlebotomist if they had to reposition the needle multiple times. A difficult draw with multiple sticks increases the risk of mechanical hemolysis. If you have a history of difficult draws, request a butterfly needle and a phlebotomist who works with athletes. This one step eliminates the most common source of false potassium and LDH elevations.
Hemolyzed samples show a characteristic pattern: elevated LDH (often > 300), high potassium (from ruptured RBCs), and elevated AST (also released from red cells). If you see this triad in an otherwise healthy person — normal kidney function, no symptoms, no recent training — hemolysis is the most likely explanation.
The Hemolysis Triad
Prolonged Tourniquet
A tourniquet left on for more than one minute causes blood to concentrate in the limb. Fluid shifts out of the veins into the surrounding tissue, concentrating the blood cells and large molecules left behind. This affects: potassium (can rise 0.3-0.5 mmol/L), total protein and albumin (up 5-10%), and hematocrit (up 2-4%). The effect is proportional to tourniquet time: every 30 seconds past the first minute adds measurable artifact.
The tourniquet effect is dose dependent. One minute of tourniquet time raises potassium by about 0.3 mmol/L. Two minutes raises it by 0.5 mmol/L. If you are already at the top of the reference range, that 0.5 can push you into the danger zone. The same mechanism concentrates total protein, albumin, and calcium. If you see a pattern of elevated protein, albumin, and potassium together, suspect tourniquet time. Ask the phlebotomist to release the tourniquet as soon as blood starts flowing. Better yet, ask for a draw without a tourniquet if your veins are accessible. Many experienced phlebotomists can draw from a good antecubital vein without one, especially in athletes with high blood volume.
Fasting Violations
A non-fasted draw is the most common preventable error. Triglycerides can spike 200-300% after a meal, making LDL calculations unreliable. Glucose reflects your last meal, not your metabolic health. Even ALT can be mildly elevated after a high-fat meal. If your triglycerides are surprisingly high but your LDL is normal and your HDL is good, a fasting violation is the most likely cause.
Fasting violations are not just about triglycerides and glucose. A high-fat meal the night before can elevate ALT by 10-20 U/L in some individuals. A high-carb meal can shift your potassium slightly due to insulin-mediated cellular uptake. Even caffeine can raise your free fatty acids and affect some assays. The standard recommendation is a 12-hour fast, water only, no coffee, no training for 24 hours. If you are on an oral AAS, your liver enzymes are already under stress. Adding a fatty meal to the mix can produce an ALT of 60-70 U/L that looks alarming but is simply a postprandial artifact. If your ALT is mildly elevated but your GGT and bilirubin are normal, ask yourself: did I fast properly? Redraw after a true fast before you change your protocol.
Lab Error vs. Real Signal: How to Tell
| Marker | Likely Lab Error | Likely Real Signal |
|---|---|---|
| Pattern | Single marker out of range, everything else normal | Multiple related markers form a consistent pattern |
| Potassium | High K + high LDH + high AST = hemolysis | High K + low GFR + high creatinine = kidney issue |
| AST/ALT | Isolated AST elevation with normal ALT/GGT | Elevated AST + ALT + GGT = liver origin |
| Lipids | Very high TG + normal LDL + non-fasted draw | High LDL + low HDL + high ApoB = genuine dyslipidemia |
| Timing | Drawn after training (elevated CK, AST, creatinine) | Consistent elevation despite 72h rest |
| Symptoms | No symptoms, feel normal | Symptoms match the abnormal marker |
| History | First time elevated, never been high before | Trending up over multiple draws |
The decision to redraw depends on the severity of the abnormality and the supporting evidence. Use this framework:
- Redraw if: a single marker is mildly to moderately elevated (less than 2x the upper reference limit), no other markers support it, you have no symptoms, and the result does not match your history. The most common example: isolated AST of 80 U/L with normal ALT, GGT, and CK. Redraw with proper rest and a clean draw technique.
- Redraw if: the lab report flags the sample for hemolysis, lipemia, or icterus. These are visible indicators that the sample quality was compromised. Do not accept results from a hemolyzed sample: they are unreliable and should be rejected by the lab before they are even reported.
- Act immediately if: potassium > 6.0 mmol/L, hemoglobin < 7 g/dL, platelets < 20,000, or any value the lab marks as "critical." Even if lab error is possible, critical values require immediate medical evaluation. You can sort out whether it was an error later.
- Act if: the same marker is abnormal across multiple draws, the pattern is consistent with your protocol (e.g., HDL is low on an AAS cycle: expected, not an error), or you have symptoms that match the lab abnormality.
A hypothetical illustration of the pattern: someone on 500 mg testosterone enanthate weekly, no orals, gets an AST of 95 U/L, ALT 28 U/L, GGT 22 U/L, CK 180 U/L. The lab flags AST as high, and it's tempting to stop the cycle and start liver support. But the pattern points to hemolysis: AST is in red cells, ALT is not. CK is normal, so it isn't muscle damage. A redraw 72 hours later with a butterfly needle, fasted, no training for 3 days, comes back at AST 32 U/L. The first draw was hemolyzed. Acting on the first result would have meant wasted money on TUDCA and a week of unnecessary worry. The lesson: always look at the pattern, not the single number.
The Redraw Protocol
One more variable to control: time of day. Cortisol and other hormones have diurnal rhythms, but even potassium and creatinine vary slightly. A morning draw after sleep is the most reproducible. If you train in the evening, a morning draw is 12+ hours after your last session, which minimizes exercise-induced CK and potassium shifts. Also, stay hydrated. Dehydration concentrates your blood and can raise creatinine, hematocrit, and total protein. Drink 500-750 mL of water in the hour before the draw. This does not dilute your blood enough to change results, but it ensures you are not in a dehydrated state. If you follow these conditions and the marker is still abnormal, then you have a real signal. That is the point where you investigate further, not before.
While lab errors are common, real problems are also common in the AAS-using population. The key is not to dismiss every abnormal result as a lab error: it is to evaluate each result in context. You should act on a result when:
- Multiple independent markers point to the same problem (e.g., elevated creatinine + low eGFR + elevated cystatin C = real kidney concern)
- The same marker is consistently abnormal across multiple draws under optimal conditions
- The abnormality matches known pharmacological effects of your compounds (e.g., low HDL on orals is expected, not an error)
- You have clinical symptoms that align with the lab finding
- The value exceeds critical thresholds: no amount of "it might be an error" excuses ignoring a critical lab value