Have you ever wondered how 98.6° Fahrenheit or 37° centigrade became “normal” body temperature? In the 1850’s, a German physician named Carl Wunderlich collected data on 25,000 patients, taking their temperature multiple times. Wunderlich was the first to show how the body temperature fluctuates naturally throughout the day and night, and he was the first to set the threshold for fever (any temperature above 100.4 F.)
But Wunderlich’s scientific method intrigued and challenged one very creative thinker. Philip Mackowiak, who is a medical doctor (internal medicine) and professor of medicine and medical historian at the University of Maryland, was interested in clinical thermometry, or the measurement of body temperature. He was able of obtain one of Wunderlich’s original thermometers.
To make a fun story short (and you can listen to the entire podcast on Freakonomics here), Mackowiak describes the thermometer as unwieldy and non-registering, meaning it has to be read while it’s in place. In addition, Wunderlich only measured armpit (axillary) temperatures, and today we know that the most accurate measurements are by mouth or better, rectal temperature. Body temperature varies from one person to another. In women, it increases with ovulation and during the menstrual cycle. During vigorous exercise temperature increases.
Wondering about the historical accuracy of “normal,” Mackowiak set up his own experiment. Mackowiak learned that a person’s temperature is “almost like a fingerprint” and is unique to the individual. In his modern study he found the actual “normal” temperature to be 98.2 degrees.
My “normal” temperature is 96.8°. What’s yours?
There are many myths associated with high blood pressure (HTN), the most important one is that if you have it, you have symptoms. But that is wrong. Unfortunately, often the first symptom is stroke, or even death.
Like type 2 diabetes, once you have HTN, if you do have symptoms like headache, nosebleeds or blurry vision, it means the HTN has reached “severe and possibly life-threatening levels” according to Dr. Daniel Pohlman, a primary care doctor at Rush University Medical Center.
The only way to know if you have HTN is to get it checked regularly. And although the risk increases with age, even children can develop it, so they should be checked routinely, beginning at age three.
But measuring blood pressure needs to be done correctly. According to Dr. William B. White, editor of the medical journal Blood Pressure Monitoring, blood pressure is measured incorrectly about 50% of the time. Nutrition Action lists common mistakes when measuring blood pressure:
- After consuming caffeine, which temporarily raises pressure
- Within 30 minutes of smoking — raises blood pressure
- If your bladder is full — raises pressure
- Within 30 minutes of aerobic exercise, such as jogging or even brisk walking — temporarily lowers pressure
- Sitting on a exam table or chair without back support — can raise diastolic (the lower number) pressure
- Sitting with legs dangling or crossed — raises pressure (keep your feet flat on the floor)
- With your arm above or below heart level. The person measuring your arm should be supporting your arm, not you
- Don’t speak — stay calm, because even casual conversation can raise pressure
One thing that can definitely raise your blood pressure is YOU! You may be like the 20% or more of patients who have “white coat syndrome”, where your blood pressure surges when measured in a clinical setting like the doctor’s office.
The Harvard Health Letter reports that blood pressure changes day to day and hour to hour, even minute to minute. They suggest that people with high blood pressure who check it consistently at home tend to be more successful in keeping it under control. Use an automatic monitor with a cuff that fits around your arm and that tracks your readings, or keep a detailed diary. Click here for a comprehensive article plus a video about the correct way to check your own blood pressure.
Two numbers represent blood pressure. The higher (systolic) number shows the pressure while the heart is beating. The lower (diastolic) numbers shows the pressure when the heart is resting between beats. According to Blood Pressure UK, ideally, we should all have a blood pressure below 120 over 80 (120/80). At this level, we have a much lower risk of heart disease or stroke.
Chronic high blood glucose is a primary risk factor for development of complications in diabetes, such as damage to nerves (leading to neuropathy), to blood vessels of the retina (diabetic retinopathy), cardiovascular disease, non-healing wounds and fungal infections, and more. Blood glucose and blood sugar mean the same thing — the sugars we eat, from fruit, lactose, starches or just simple carbohydrates are all converted into glucose, which provides fuel for our body. We need insulin, a hormone released from the pancreas, to “unlock” the cells so the glucose can be utilized.
Prevention of type 2 diabetes, which affects 80%-plus patients with diabetes, may be possible with lifestyle modification, weight loss and consistent activity. Testing frequently is essential to good health. After all, what you don’t know can hurt you, but when you know there’s a problem, you can take steps to solve it.
Normal blood glucose numbers
Normal for person without diabetes: 70–99 mg/dl (3.9–5.5 mmol/L)
Official American Diabetes Association recommendation for someone with diabetes: 80–130 mg/dl (4.5–7.2 mmol/L)
2 hours after meals
Normal for person without diabetes: Less than 140 mg/dl (7.8 mmol/L)
Official ADA recommendation for someone with diabetes: Less than 180 mg/dl (10.0 mmol/L)
HbA1c Hemoglobin A1c is blood test that shows your average blood glucose over the previous 2-3 months.
Normal for person without diabetes: Less than 5.7%
Official ADA recommendation for someone with diabetes: 7.0% or less
Have your blood glucose tested on a yearly basis, especially if you have risk factors for type 2 diabetes, including a family or personal history of high blood glucose and/or diabetes, if you’re overweight or obese, and if you’re sedentary and have symptoms (blurred vision, unexplained weight loss, unusual thirst, slow wound healing, fatigue.)
Some blood glucose monitors are more accurate than others, but experts say that technique is typically the reason for inaccurate readings. There are a number of factors that can affect accuracy:
- Damaged or outdated test strips
- Extreme temperatures: keep meter and strips at room temperature
- Proper coding: some meters must be coded to your particular test strips
- Monitor use/functionality: make sure you’re inserting the strip properly, and that the batteries are up to snuff.
- Sample size: most monitors need a generous drop of blood to get an accurate reading.
- Red blood cell count: dehydration can skew your numbers; if you have anemia the reading is likely to be less accurate.
A good idea is to bring your monitor with you to your next doctor’s appointment or when you’re going to the lab for new tests. Check your own blood glucose level with your meter at the same time as you’re getting blood drawn for your tests. Results within 15% of the lab reading are considered accurate.
Blood Pressure UK. What is normal blood pressure? http://www.bloodpressureuk.org/BloodPressureandyou/Thebasics/Whatisnormal
CuencaHighLife.com. Is there a cure for diabetes? https://www.cuencahighlife.com/is-there-a-cure-for-diabetes/
Diabetes Self-Management. What is a normal blood sugar level? http://www.diabetesselfmanagement.com/blog/what-is-a-normal-blood-sugar-level/
Freakonomics Radio. Bad Medicine, Part 1. The Story of 98.6 http://freakonomics.com/podcast/bad-medicine-part-1-story-98-6/
Harvard Health Letter. Checking blood pressure: Do try this at home. http://www.health.harvard.edu/heart-health/checking-blood-pressure-at-home
JAMA Network. A critical appraisal of 98.6°, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August Wunderlich. http://jamanetwork.com/journals/jama/article-abstract/400116
MayoClinic.org. Diabetes. Sometimes my blood glucose monitor seems to give incorrect readings. What can I do to make sure the measurement is accurate? http://www.mayoclinic.org/diseases-conditions/diabetes/expert-answers/blood-glucose-monitors/faq-20057902
Nutrition Action. Don’t let your doctor make these 9 blood pressure measurement mistakes. http://www.nutritionaction.com/daily/heart-and-disease-cat/dont-let-your-doctor-make-these-9-blood-pressure-measurement-mistakes/
Rush University Medical Center. Myths about high blood pressure. https://www.rush.edu/health-wellness/discover-health/high-blood-pressure-myths
University of Michigan Health System. Body Temperature. http://www.uofmhealth.org/health-library/hw198785