Aidan:
Hello and welcome to episode 230 of the Ideal Nutrition podcast. My name is Aidan Muir, and I’m here with my co-host Torwen Eerkins. And today we’re talking about blood tests we recommend getting. We are going to be splitting this into three categories. We’re talking about nutrients.
We’ll have a section on metabolic and miscellaneous, like metabolic conditions and similar. And then we’ll have a section on hormones. We might touch on specific conditions within there as well. For starters, I would always get a doctor to include the things they naturally include anyway. I wouldn’t say, only get these ones.
I’d get them to include what they usually include. I just think in many situations, I’d also want them to include other things if relevant. We’re going to start with the nutrient section and go back and forth. Do you want to go first, Torwen?
Torwen:
Yeah, the big one, and I think this is fairly important for most people, is iron. So do full iron studies: ferritin, serum iron, transferrin, and TIBC. We know low ferritin is associated with fatigue, brain fog, and low exercise tolerance.
Aidan:
I’m really big on that. It’s hard to feel good if you have low iron. And it’s a big one to adjust. It’s also very prevalent. Very worth doing. Another one, and I’ll lump two together, is vitamin B12 and folate. These are important for energy. That’s why you can get anaemia with low B12. They also relate to red blood cells and neurological health.
These might be more common in people who are plant-based. We also know with B12 that absorption gets worse as people get older. Above about the age of 70, deficiencies or near-deficiencies are surprisingly prevalent.
Torwen:
Cool, the next one I’ll say is vitamin D. We know it’s important for bone health, immunity, and mood regulation. Here, I’d definitely consider it if you’re an office worker and inside a lot. Consider it if you’re older and outside less, or in winter. It’s easy to supplement and can make a big difference.
Aidan:
Some things I’m less concerned about, from the nutrient perspective, are magnesium and calcium as intake markers. They aren’t reflective of intake due to homeostasis. For example, if the calcium in your blood drops too low, your body pulls calcium from your bone. Your blood levels can still look good while osteoporosis risk rises.
If calcium levels are high from food in the gut, you’ll absorb less. Mechanisms keep it within range. If it goes out of range, it’s less about intake and more about other issues. Potentially, kidney issues, for example.
Torwen:
I’m going to add zinc, as it’s important for immune and wound function, and hair growth. Especially if I was seeing a client who has a lower intake or a restrictive diet. I’d add this to consider.
Aidan:
I’ve been talking more about zinc intake when people supplement. There are many benefits if intake is otherwise low. If someone supplements, I’d be cautious of going too high. I think 50 milligrams per day is fine short-term. Long-term, that’s potentially risky because it can lead to copper deficiency. Because they compete for absorption. A higher dose short-term can be useful if it is addresses something. I’d be cautious about doing that year-round.
Torwen:
Cool, anything else you want to add?
Aidan:
No, let’s talk metabolic stuff.
Torwen:
Amazing. I’m going to start with the big one, glucose. Get fasting glucose and HbA1c to assess blood sugar control and insulin sensitivity. We can see elements of type 2 diabetes or type 1 diabetes. We can see how that impacts blood sugar control.
Aidan:
So, HbA1c helps because it reflects a roughly three-month average. It links to red blood cells, which live for around three months. You can assess if blood glucose levels are elevated. We want to be on top of that to predict pre-diabetes early. And the quicker you address it, the better. It’s possible to reverse type 2 diabetes, even if it is quite progressed. Earlier intervention makes outcomes better. The next one, in the same vein, is cholesterol and triglycerides.
You want to be on top of these as well. There are also varying ranges here. So, I’ll just talk total cholesterol for a second. There is a lot more nuance here. We could do an entire episode on this. Often you’ll hear 4.0, 5.5, and 6.0 mmol/L discussed. Some doctors call 5.5 or above high. Some call six or above high. There are categories like primary and secondary prevention. Primary prevention sits around 4.0. Secondary prevention sits around 6.0.
And it is food for thought, you could be at 5.9 and not be considered high. It still sits far from primary prevention targets. Going deep on longevity, there’s a reason statins tank LDL cholesterol very low. One of the biggest things is it just reduces cardiovascular disease risk. Regardless of opinions on statins, keeping LDL lower is a good idea.
Torwen:
Next I’ll talk about liver function tests. So, ALT, AST, and GGT. We also sometimes look at ALP and bilirubin. These can detect inflammation or potential fatty liver. Findings can guide whether to support weight loss or liver function.
Aidan:
And, kidney function tests as well. So, creatinine, urea, and eGFR. On most reports, eGFR uses a formula based on creatinine. Creatinine is the main driver of that estimate. I have two things to add about kidney and liver function tests. If you train hard. And many listeners probably train hard. A blood test soon after hard training can show elevated liver enzymes. The same thing goes for creatinine as well. More muscle mass can also raise creatinine.
A hard session breaks down creatine to creatinine in the blood. Therefore, creatinine can be elevated. These can be false markers in that context. Training hard is fine and not detrimental to health. Research shows training hard doesn’t cause long-term issues in these markers. But, it can still be misleading on a blood test.
For the most accurate result, do at least a deload week. You could even take a full week off. There’s a study where non-lifters did one hard weights session. Their liver function tests stayed elevated a week later. Crazy, isn’t it? In my clients, I mostly see this among absolute monsters of training. They train really hard. Many people freak out after a test. It’s sometimes just training within a few days of the test.
Torwen:
That’s an interesting point. I wasn’t fully aware of that. There you go. The last one I’ll add is CRP, or C-reactive protein. It’s a marker of systemic inflammation. It can be elevated with chronic disease. And it can also reflect poor recovery, generally. We see values from very low to extremely high in acute illness. Values can sit lower, or in between, with chronic disease.
Aidan:
I often see this discussed in the evidence-based community. When someone posts that they’re inflamed, people ask how it was measured. Has CRP been elevated and measured? It’s worth thinking about that. When someone says they’re inflamed, sometimes it’s inflammation. Sometimes it’s pain, like joint pain.
Is that inflammation or joint pain? Sometimes there’s swelling, bloating, or other issues. But there are legitimate blood measures of inflammation we can look at. Now we’re going to talk about hormones. So, there are a few things. Where do we want to start with hormones?
Torwen:
Should we start with thyroid?
Aidan:
Yeah, happy with that.
Torwen:
Looking at TSH, free T4, and free T3 gives a good indication of thyroid function. Thyroid function is important for metabolism, energy, and weight regulation. So, knowing those levels helps support care.
Aidan:
That gets into the first conditions, hypothyroidism or hyperthyroidism. Hyper is a faster thyroid. Hypo is down-regulated. The body doesn’t burn calories for no reason. It links to functions that use energy. If functions burn more calories, they usually do more work. With hypothyroidism, we see markers out of range. But then, that often leads to symptoms. Those symptoms then change energy expenditure.
If the gut slows down, fewer calories are spent on digestion. You might get constipation as a symptom. If core body temperature decreases, you feel colder. Their metabolism spends fewer calories on heating the body. Fewer calories get burned there. This becomes interesting in practice. Say I’m working with someone with Hashimoto’s or hypothyroidism. We’re concerned their metabolic rate is lower due to this.
Research is consistent that if thyroid hormones return to range, metabolic rate looks similar. That’s compared to people without Hashimoto’s or hypothyroidism. The tricky part is that medication dosing often needs adjustment over time. It might go too high or too low. You might get a blood test and hormones are still suppressed. You may or may not need more medication to return to range.
Torwen:
Should we chat about sex hormones?
Aidan:
Yeah.
Torwen:
So, if we’re at female hormones, we look at progesterone, oestrogen, FSH, and LH. These play roles in the menstrual cycle. We can look at estradiol to track oestrogen status. That’s relevant for cycle regulation and menopause. It can also indicate bone health. The same goes for progesterone. It tells us the cycle phase we’re in. Low levels can contribute to higher PMS anxiety or poor sleep.
Aidan:
The good thing about blood tests is that they often include reference ranges. Women’s hormones are more complicated, with ranges by cycle phase. On the test, the ranges are split by phase. If oestrogen looks high for one phase, it could be normal for another. These hormones bounce around, so ranges help. If values sit outside all phase ranges, that’s more concerning. That could prompt action.
Torwen:
Do you ask clients what phase they’re in when reviewing these?
Aidan:
Yeah, it’s often noted down. Let’s talk testosterone now. It can bounce around a fair bit. There are ranges we want it within. We have free and total testosterone. In women, we might check it when assessing for PCOS. Elevated testosterone is part of diagnostic criteria. In men, I don’t check testosterone for everyone. If symptoms suggest low testosterone, it’s worth checking. Options include nutritional changes to address it. We could also consider hormone replacement therapy if suitable and of interest.
Torwen:
Anything you wanted to add?
Aidan:
I don’t think so. I think that’s covering most.
Torwen:
Amazing. Well, this has been episode 230 of the Ideal Nutrition podcast. We hope we’ve given insight into the blood tests that we recommend. If you enjoyed this episode, please leave a positive review. And we’ll be back next week.