“Hemolysis” on a Blood Test: Causes and Retesting

If your blood test results say “hemolysis,” in most cases it means red blood cells broke apart inside the tube after your blood was drawn. This is called sample hemolysis. Sample hemolysis itself isn’t a sign that anything is wrong with your body, but it can make potassium, LDH, and AST read higher than they really are, so you may be asked to retest (have your blood drawn again). Separately, there is also hemolysis in the body, where red blood cells break down sooner than usual. It’s less common, but sometimes the “hemolysis” on your results reflects this instead.

What hemolysis is: red blood cells breaking and spilling their contents

Red blood cells are the cells that carry oxygen throughout the body. They live for about 120 days, and old red blood cells are taken up and broken down mainly by macrophages (cells that take in and dispose of old cells and the like) in the spleen and liver. The heme part of hemoglobin is broken down into indirect bilirubin, which the liver then processes. The iron is pulled out and reused to make new red blood cells. All of this is the normal turnover that happens every day.

Hemolysis refers to the membrane of a red blood cell breaking so that its contents, such as hemoglobin, potassium, and enzymes, spill out. When this word comes up around blood tests, it means one of two things:

• Sample hemolysis: red blood cells broke inside the tube sometime between the blood draw and the measurement
• Hemolysis in the body: red blood cells are breaking down inside the body at a faster pace than usual

A “hemolysis” comment on the results of a checkup or a comprehensive health screening (what Japan calls a ningen dock) almost always means the first kind. Telling these two apart is the starting point for making sense of the word “hemolysis.”

“Hemolysis” on your results: think of sample hemolysis first

Sample hemolysis is common

Sample hemolysis is known as the most common reason samples that arrive at a lab turn out to be unsuitable for testing. One report puts it at as many as 3.3% of routine samples at some sites, and it’s said to be even more frequent in samples from emergency departments.

Most of the causes lie in how the blood is drawn and handled afterward:

• A thin needle or strong suction put stress on the red blood cells
• The tourniquet (the band tied around your arm) was left on for a long time, or the draw took a while, for example because the needle had to go in again
• The tube was shaken hard
• The sample waited a long time before being spun in the centrifuge, was exposed to heat or cold, or was jostled in transit

Markers most likely to be affected

Substances found in much higher amounts inside red blood cells than in serum leak into the serum when red blood cells break in the tube, so they read higher than their true values. The main ones are potassium, LDH, and AST, and serum iron, magnesium, and phosphorus can also read on the high side. On the other hand, some markers, such as ALP and sodium, can read lower. ALT is also found inside red blood cells, but the gap in concentration between the cells and serum is smaller than for AST or LDH, so hemolysis affects it relatively little. Also, a hemolyzed sample takes on a reddish tint, which can throw off the measurement itself for some markers that are measured by color.

If you’re asked to retest

Recommendations from a working group of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) suggest measuring the degree of hemolysis with an analyzer, adding a comment to the result when the effect is small, and withholding the result and asking for a new blood draw when the effect is large. In Japan, how this is handled varies from lab to lab.

Being asked to retest means the result may not accurately reflect what’s going on in your body. It doesn’t mean a disease has been found. If sample hemolysis was the cause, your numbers will settle down once the test is redone under the right circumstances.

Hemolysis in the body

Hemolysis in the body means red blood cells are surviving for a shorter time than usual. There are many possible causes, including inherited traits of the red blood cells, the immune system, infections and medications, and physical forces such as those from an artificial heart valve. If you’re wondering about a medication you take, don’t stop it on your own; talk with the doctor who prescribed it or your pharmacist. Exercise that puts repeated impact on the soles of the feet, such as running, has also been reported to break red blood cells.

Finding out whether hemolysis is happening in the body, and what’s causing it, is a job for a doctor.

Markers that shift with hemolysis in the body

When hemolysis keeps happening inside the body, you may see changes like these together:

• Indirect bilirubin rises (because more hemoglobin is being broken down)
• LDH rises, and AST may rise slightly too
• Haptoglobin (a protein that binds to hemoglobin released into the blood) falls
• Reticulocytes (young, newly made red blood cells) increase, though they may not if, for example, iron, vitamin B12, or folate is in short supply
• Hemoglobin falls if red blood cell production can’t keep up

However, every one of these markers can also shift for reasons other than hemolysis. No single number can tell you that hemolysis is happening.

Sample hemolysis and hemolysis in the body move the numbers differently

The clearest differences tend to show up in haptoglobin, potassium, and indirect bilirubin, and in whether you get the same result when you retest. Sample hemolysis happens inside the tube, so it doesn’t come with changes that can only happen in the body, such as a drop in haptoglobin or a rise in bilirubin or reticulocytes. That said, haptoglobin can fall without any hemolysis, for example with liver disease, and with strong hemolysis, the bilirubin number can appear shifted depending on the measurement method. The table sums up general tendencies; confirming which kind applies to you is up to your doctor.

Reference ranges for related markers

Reference ranges vary by facility and measurement method, so first check the range printed on your own results. For reference, here are the main hemolysis-related markers in Japan’s shared reference intervals (JCCLS):

• LDH (LD): 124–222 U/L
• AST: 13–30 U/L
• ALT: men 10–42 U/L, women 7–23 U/L
• Potassium: 3.6–4.8 mmol/L
• Total bilirubin: 0.4–1.5 mg/dL

In Japan, the measurement method for LDH changed to the IFCC method around 2020, but the shared reference interval is the same under either method. Indirect bilirubin and haptoglobin aren’t included in the shared reference intervals, so use the reference range from the facility where you were tested.

How I read the numbers

What follows isn’t a medical standard; it’s how I read blood data from a precision nutrition perspective. Rather than stopping at whether a value is inside or outside the reference range, I pay close attention to where it leans within the range and how the markers combine.

For the main markers in this article, the precision nutrition optimal ranges I use in my counseling are as follows. These are precision nutrition guides, not medical reference ranges.

For potassium, mEq/L and mmol/L give the same number. The top of the optimal range (5) is above the upper limit of the shared reference interval (4.8 mmol/L), but if your potassium is above the reference range printed on your own results, the first step is to have a doctor check it, even when it’s within the optimal range. Falling outside these optimal ranges doesn’t by itself mean you have an illness.

Reading it alongside other markers

First, I check whether there’s a “hemolysis” comment on the results. Then, if LDH and AST are in the upper part of the reference range while ALT hasn’t gone up, and potassium is on the high side too, I consider the possibility of sample hemolysis. However, if potassium is above the reference range, don’t assume it’s sample hemolysis; the first step is to have a doctor retest it soon.

If CK is high as well, I also consider strain on the muscles from intense exercise. At the same time, I look back on whether the blood draw took a long time, and whether there was any intense exercise in the few days before the test. In the study used to set the JCCLS shared reference intervals, too, participants were asked to avoid intense exercise within 3 days before the blood draw, because LD, CK, and AST rise with intense exercise.

On the other hand, if potassium is steady but LDH and indirect bilirubin lean toward the upper part of the reference range, and that continues even after retesting, I also consider the possibility that red blood cell turnover in the body has sped up. When vitamin B12 or folate runs short, immature red blood cells can also break down in the bone marrow, which can likewise raise LDH and indirect bilirubin and make MCV (red blood cell size) larger. In that case, I look at hemoglobin, MCV, reticulocytes, and ferritin as well, and take it as a cue to suggest talking with a doctor. I explain how to read LDH itself in my LDH article, and how to read iron in my iron and ferritin article.

The optimal range for indirect bilirubin, and a caution

When indirect bilirubin goes above 0.6 mg/dL, the top of the optimal range, I take it as a cue to check other markers along with it. This isn’t a medical standard.

Indirect bilirubin can rise even without hemolysis: for example, with an inherited trait in which the body processes bilirubin a little more slowly (Gilbert’s syndrome, thought to affect anywhere from a few percent to about 10% of people), or after a long stretch without eating. If your liver markers and red blood cell counts are steady and only bilirubin is a little high, this trait may be the reason. A doctor can check whether you have it.

Look into the cause before turning to nutrition

If hemolysis may be ongoing in the body, the priority is to have a doctor look into the cause before trying to handle it with nutrition. The part precision nutrition can play builds on your medical results and your doctor’s plan: helping you find your balance in the nutrients your body uses to make red blood cells, and in how much strain you put on your body.

What you can revisit in everyday life

Before and on the day of your blood draw

• Avoid intense exercise for at least 3 days before your blood draw, and leave about a week after any exercise you’re not used to
• Drink water as usual, unless you’ve been told to limit it
• If you know your veins are thin or that your blood draws tend to take a while, let the person drawing your blood know
• If you want to compare with last time, keep the time of day and your meals the same

Food and exercise

Making red blood cells takes protein, iron, folate, vitamin B12, and more. The basic approach is to get these from your everyday meals in a balanced way, along with vitamin E (plentiful in nuts, vegetable oils, eel, and fish roe) and vitamin C (plentiful in vegetables and fruit). However, there’s no evidence that healthy people reduce hemolysis by taking in more of these nutrients. On the contrary, there are reports of hemolysis caused by large amounts of vitamin C, seen mostly when it was given by IV or in people with an inherited trait called G6PD deficiency.

If you regularly run long distances, it helps to know that the impact of landing can break red blood cells, and that the strain on your muscles can raise LDH, AST, and CK. Knowing this changes how you read your results. Look back on whether your test fell during a period when you were running a lot.

If you’re concerned

• If your results say “retest due to hemolysis,” start by having your blood drawn again as instructed.
• If you notice shortness of breath, a racing or pounding heart, strong fatigue, yellowish skin or whites of the eyes, or urine that has turned a dark reddish brown, talk with a doctor without waiting for test results.
• If results such as high LDH or indirect bilirubin, or low hemoglobin, continue even after a new blood draw, bring your results to a doctor, such as an internist, and talk it over.
• If you’re already under a doctor’s care, follow your doctor’s plan first.