Latest / Common Sense Health / Don't Let Blood Test Jargon Confuse You: A Simple Guide to mg/dL and mmol/L
Transcript
- Stephen Thomas BSc. Hons: Hello. Concentration is one of those science words that can sound more complicated than it really is. It has the sort of name that makes people immediately think, well this is going to involve equations or a whiteboard and possibly emotional damage. But the basic idea is actually very simple. A concentration tells us how much of one thing there is compared with how much of something else. That's it. If you dissolve something into a liquid The thing being dissolved is usually called the solute, and the liquid it is dissolved into is called the solvent. Put them together and you have a solution. So for example, if you dissolve one gram of aspirin into one liter of water, you have a concentration of one gram per liter. And the important point here is the concentration is a ratio. If you dissolved half a gram of aspirin into half a litre of water, the concentration would still be one gram per liter. If you dissolved 10 grams of aspirin into 10 litres of water, again, the concentration would still be 1 gram per liter. Now, this is one of the big things people often miss. Concentration is not the same thing as the total amount. If you have a little a liter of orange squash and you pour half of it away, the remaining half does not suddenly become stronger or weaker. The concentration is the same. You simply have Less total squash to drink. Now that distinction matters far more than people realise, especially when we start talking about blood tests. A concentration is a relationship. It tells us how much of something is present relative to the volume or amount it is in. It does not necessarily tell us the total amount in the whole body. Let's use a very simple example. Imagine three glasses of water. Into the first glass you add a tiny splash of black black current squash. Into the second you add a So look look look look and into the third you add the amount a child would add if they were left unsupervised for about nine seconds. Now the colour of the liquid gets deeper as the concentration of squash increases. The first glass may look very pale, the second may look like normal squash, and the third one may look like something that could strip paint off a garden fence. Now that's the important thing that as the concentration increases, the colour becomes stronger. And we can use that relationship in reverse. If the colour intensity changes in a predictable way as the concentration changes, then by measuring the colour intensity, we can estimate the concentration. And that basic principle is used in laboratory measurement. The machine does not look at your blood in in the way you or I would look at a glass of squash, but the broad idea is similar. This is what we talk about. There is a measurable signal. The signal changes according to the concentration of the substance being measured. The machine detects the change and calculates a number. In many laboratory methods, light is passed through a sample, or a chemical reaction produces a colour change, or some other signal is generated, and the analyzer compares that signal against known standards and reports the concentration. So, in plain English, more dissolved substance often means a stronger signal. And this is why machines are so useful. They're not guessing, they're measuring a signal and comparing it with known concentrations. So far, so simple. Then units walk into the room wearing hobnell boots. I'm not saying units, by the way, I'm saying units. Because concentrations are not really that difficult to understand, but units are where things can become confusing. You can express concentration in lots of different ways. You can have grams per liter, you can have milligrams per deciliter, you can have millimoles per liter, or you can have a percentage weight per volume, or you can have parts per million, or parts per billion. You can even have something called a mole fraction, which sounds like the sort of thing that should be kept in a locked cabinet. But then we come to blood testing itself. We run into extra fun that different countries often report the same marker using different units. A very common example is blood glucose. In the UK blood glucose is commonly reported in millimoles per liter written as MOL dash L, and in the US blood glucose is often reported in milligrams per deciliter, written as MG slash DL. But it's the same biological reality. It's just a different measuring language. It is a bit like saying someone is six feet tall or 183 centimeters tall. The person has not changed height, you have just changed the unit. So when you see mg-dL, that means milligrams per deciliter. Now a milligram is a unit of mass and a deciliter is one tenth of a liter. So if someone has glucose of 90 mg-dL, that means there are 90 milligrams of glucose in each deciliter of blood. Now when you see mmol. L that means millimoles per liter. Now this is different because instead of focusing directly on the weight of the substance, it is relating to the number of particles or molecules present or things. And this is why conversions between milligrams per deciliter and millimoles per liter are not always the same for every blood marker. So to convert properly, you need to know the molecular weight of the substance being measured. So that means glucose or cholesterol or triglycerides or sodium or calcium or magnesium and you know uric acid, they all have their own conversion relationships. There is no single universal multiply by this conversion that works for every blood marker. Biochemistry annoyingly refuses to become like a fridge magnet. Next we come to some terminology that you may have heard, but perhaps never. properly had explained to you, such as the term mole. You may have seen this in the context, like I say, of blood glucose being reported as, for example, five millimoles per litre. So what is a mole? Well a mole is simply a way of counting very tiny things. Think of the word dozen, right? A dozen means twelve. A dozen eggs means twelve eggs. A mole is similar except instead of meaning twelve, it means six point two times ten to the twenty three. I mean that is approximately six hundred and two with twenty one zeros after it. that number is called Avogado Gadro's number, by the way. So one mole of glucose, one mole means six point two times ten to the power of twenty three glucose molecules. And the reason we need such a huge number is because atoms and molecules are unbelievably small. I mean try try. counting molecules individually, it'd be like trying to count every grain of sand on earth using a teaspoon and you'd end up with a nervous breakdown, I think. So for scale, one mole of jelly beans would be a planet sized amount. That's right. There's so that'd be so many basically be described as the size of the earth, basically. It's n it's not the sort of thing you'd pop in a jar on the counter in your kitchen. Now the point of that analogy is to get across the sheer size of the number That's just one mole of jelly beans. At the same time, the extraordinarily smallness of molecules is the other thing. It's not just that it's a big number, but they're obviously very small. So a mole is a massive counting unit because the things being counted are so minuscule, so tiny. And that is why in blood testing we often use millimoles. A millimole is one thousandth of a mole. So when your glucose is measured in millimoles per liter. We're talking about vast numbers of glucose molecules, but expressed in a practical laboratory unit. And this is where it starts to become useful. If your fasting blood glucose is 5.0 millimoles per litre in the UK, the same result would commonly be reported in the US as about 90 milligrams per deciliter. Now for glucose, the rusk the rough conversion is to multiply it by 18. So 5.0 times 18 gives you about 90. So that's where we get 90 milligrams per deciliter equals 5 millimoles per liter. And this is why someone in the UK might look at their result and see a glucose of 5, while someone in the US sees it as 90. Yet they are essentially looking at the same glucose concentration, just they're expressed in different units. So there's no panic required, just different measuring languages. But this is the important bit. The glucose conversion factor does not apply to everything else. For cholesterol markers, including LDL cholesterol and HDL cholesterol, the commonly used conversion is approximately millimoles per litre multiplied by 38.67, and that gives you milligrams per deciliter. So an LDL cholesterol concentration of five millimoles per litre would be approximately five multiplied by thirty-eight point six seven. Which gives you about 193 milligrams per deciliter. Now for triglycerides, the conversion is different again. For triglycerides, millimoles per liter multiplied by 88.57 gives you milligrams per deciliter. So triglycerides of 1 millimole per liter would be approximately 88.57 milligrams per deciliter. And the reason these conversion factors are different is because these Molecules have different molecular weights. The relationship between weight and number of particles or molecules changes depending on what molecule we are talking about. This is exactly why the mole is useful. It allows chemists and biochemists to think in terms of numbers of molecules, not just the mass or weight of a substance. And this brings us to one of the easiest ways people confuse themselves with blood results, comparing numbers without checking the units. For example, glucose of five point five millimole per liter and glucose of ninety nine milligrams per deciliter are effectively the same kind of result, it just expressed differently. But if someone sees five point five in one place and ninety nine in another, they may think one is dramatically larger than the other, and it's not. All that's happened is the yard the the yardstick has changed. The same thing happens when we compare cholesterol results across UK and UK. USA content. A total cholesterol of 7 millimoles per litre may sound very different from 270 milligrams per deciliter, but again, these are two expressions of the same concentration. And this is why screenshots, online disc discussions, and social media debates can quickly become a biological food fight. Before interpreting a result, we always need to ask a few basic questions. What marker is being used? What unit is being used? What is the clinical context? Is the person eating a low carb ketogenic or carnivore diet? Has the result changed over time is a really good one? that context actually matters enormously. And interpreting bloods in the context of a carnivore or ketogenic way of eating is crucial. What was the hydration status, which has a huge impact on dilution and concentration? What's the metabolic background? Can the well that can change the meaning of a result, especially when we are looking at glucose, insulin, triglycerides, HDL. cholesterol, LDL cholesterol, ketones, uric acid, thyroid markers and kidney markers. You know, we should be looking at those together rather than isolated. Now joined up thinking beets isolated number watching every time. Blood glucose is a very good example because many people are familiar with it. A fasting blood glucose result is a concentration. It tells us how much glucose is present in the blood sample at that moment relative to the volume of blood. It does not tell us the total amount of glucose though in the entire body. A large person and a small person could have the same blood glucose concentration, but the total amount of glucose distributed throughout the body may actually differ quite considerably. The blood result is still useful because the concentration is what? The blood vessels, the nerves, the kidneys themselves, and metabolic systems are being exposed to. And this is why concentration does matter biologically. The body is not just dealing with how much stuff exists somewhere, it is dealing with concentrations in fluids, in tissues, and various compartments. And that is what the cells experience. That is what enzymes respond to. That is what transporters, receptors, and organs have to regulate. Now, when talking about longer-term glucose exposure, we often Come to this HBA1C reading. Now, HBA1C is commonly used as a marker of average blood glucose exposure over roughly the previous two to three months. It's not a direct glucose concentration in the same way that a faster glucose measurement is, but it is related to glucose exposure over time. However, whenever HBA1C is discussed, it is also worth mentioning the fructosamine assay. Fructosamine reflects a shorter window, roughly the previous two to three weeks. Because it measures the glycated serum proteins rather than glycated hemoglobin. Now this can make it particularly useful when someone has recently changed their diet or lifestyle and wants a more responsive marker. If someone has gone low carb or ketogenic or carnivore, waiting three months for an HBA one C to fully reflect the change may feel like watching paint dry in a damp shed. Whereas fructosamine can give a shorter term view, and it's more reliable, by the way. And ketones are another ex example of concentration in blood testing. Blood beta hydroxybutyrate is usually measured in millimoles per litre. So a reading of 0.5 millimoles per litre, or 1 millimole per litre, or 3 millimoles per litre, tells you the concentration of ketones in the blood at that moment. But again, context matters. A ketone reading is influenced by fasting duration or carbohydrate intake, protein intake, obviously, exercise, stress. stress hormones, or although I prefer to call them homeostatic hormones, energy demand, metabolic flexibility, and whether someone is fat adapted. So a person eating a ketogenic or carnivore diet may not always show sky high ketones, especially if they are effectively and efficiently using them. Lower circulating ketones do not automatically mean not working. Sometimes it may mean production and utilization are pretty well matched. The bloodstream is a transport system, not a trophy cabinet. So we can move on to electrolytes. Electrolytes are another excellent example. Electrolytes such as sodium or potassium or chloride or calcium and magnesium are often reported in millimoles per litre. Now this makes sense because these substances act as charged particles in solution. Their concentration affects nerve function, muscle contraction, fluid balance. Heart rhythm and cellular function. So a small change in concentration can matter biologically. Sodium, for example, is tightly regulated. You can drink more water, sweat more, eat more salt, or lose fluid, but the body works hard to maintain sodium within a sort of fairly narrow range. This is another reminder that blood raw blood results are not just numbers on paper, they are just snapshots of the body's regulation. Concentration does not tell the whole story. A blood concentration tells us what is present in the blood sample. It does not always tell us how much is stored in tissues. It does not always tell us how much is being used. It does not always tell us how quickly something is being produced. And it does not always tell us how quickly something is being cleared either. It does not always tell us whether that level is appropriate for the person's physiology. And it certainly does not tell us whether the reference range is ideal. For that person's context. And this matters when looking at markers such like ferritin or vitamin B twelve thyroid hormones, definitely with glucose and insulin, uric acid, and lipids. A concentration is a clue. It is not the entire sort of detective novel. This is always why I always say about laboratory machines being so useful because machines are very good at measuring the signals. Like I say, a sample goes in. Light, electricity, chemistry, antibodies, enzymes, or sensors produce a measurable response, and that response is compared with standards of known concentration. The machine then calculates the concentration in that sample. But that brings me back to that glass of squash. If you know what weak squash or medium squash and strong squash look like, you can compare an unknown glass and estimate where it sits. So laboratory analysers use far more precise versions of that sort of broad principle. They compare the unknown sample against known standards and convert that signal into a reported concentration, which is pretty clever. And slightly less sticky than black current squash. So the key measure is this. Concentrations are not complicated at heart, they they answer a simple question. How much of this thing is present compared with this amount of fluid or solution or sample? But blood testing becomes confusing when people forget that different units can describe the same reality. Like I say, a glucose of five millimoles per litre and a glucose of ninety milligrams per deciliter are not different metabolic universes. They are the same kind of measurement expressed through different systems. And a mole is just a counting unit, like a dozen, except instead of twelve things it measures six point two times ten to the power of twenty three. That enormous number is needed because molecules are so tiny. And when we apply this to blood testing, we get a much better appreciation of what the lab is actually reporting. We don't get vague levels, not random numbers, but concentrations, ratios, measurements, and signals that need interpreting in context, especially in the people eating low carb, keto or carnival diets, because that context is not an optional thing. It is the difference between understanding the result and simply being frightened by a bold text on a lab report. So the next time you see millimoles per litre or milligrams per deciliter or some other unit trying to ruin your afternoon, remember that glass of squash. More colour, more concentration. Different unit, same drink. And if anyone offers you a mole of jelly beans, politely declined because you will need a pantry the size of the earth. Anyway, hopefully you found that both informative and entertaining. Do try my best. And if you didn't, well I do apologize, but if you did, can you please make sure that you subscribe? If you have already subscribed, just double check that you're still subscribed, it is free and does help the channel. If you'd like to drop a comment, that would be great. If you want to give me a like or even share, then those things also help to get these videos watched and around for other people to enjoy. And if you didn't enjoy it, well drop me a comment on what you didn't like about it, and I'll try and improve the next video. Anyway, until then, I'll be back.