The Covid-19 pandemic has led to the widespread use of home monitoring devices. Wearable monitoring devices such as smart watches and fitness trackers are becoming a growing fashion amongst youth. Thermometers, glucometers, and blood pressure apparatuses are being used by households for quite some time. More and more people are getting tested from their homes and are receiving their reports on their smartphones. People are able to monitor their temperature, pulse rate, oxygen saturation levels, blood pressure, blood glucose, ECG, and many other blood parameters anywhere and anytime.  

While these technologies help people to monitor their health parameters themselves, they also have the potential to cause unintended harm. Doctors spend years of training and practice to understand human health, disease, and the appropriate use of various monitoring devices and tests to diagnose and plan treatments. It requires proper knowledge and skills to interpret the various parameters that the test results throw up. Lay people have limited and varied levels of understanding these. 

Doctors interpret various vital signs and lab reports in a given clinical context (age, gender, education, occupation, presentation of symptoms and signs, known diagnoses, past procedures, current treatment, habits, menstrual history in females etc.). Despite many years of training and experience, doctors themselves can err in their interpretation. It is only understandable that people without any medical training, can misinterpret these vital signs and reports. Misinterpretation leads to anxiety. Anxiety can lead to unnecessary self-medication, an unwarranted change in drugs or a change of a doctor or rushing to a hospital even if it may not really be required. 

Except body temperature, other vitals have a range of normalcy. For example, pulse rate can vary from 60 to 100 per minute in normal people. Systolic (upper) blood pressure can range from 100 to 140 mmHg in normal state. A rise in heart rate is normal with physical or mental exertion. Heart rate can go up to 180 beats per minute when a person sprints to catch a bus. During a treadmill stress test, the heart rate is allowed to rise to maximum expected rates (220 minus age). Systolic blood pressure responds in the same way. Any form of mental stress or excitement activates the sympathetic nervous system which causes the heart rate and the blood pressure to go up. These are normal physiological stress responses of the body. 

Lab reports also need to be interpreted in a given clinical context. Every lab report carries a normal range of values and the values which are outside of normal are highlighted. People tend to be drawn to these highlighted values. The immediate thought that crosses their mind is that they have a health problem because the value is outside of the normal range. They immediately get on to Google to diagnose their problem. It is human tendency to imagine the worst possible disease that abnormal values may correspond to. 

While abnormal values may be real, often the values may be erroneous due to faulty devices, defective lab equipment and reagents, and laboratories that lack proper quality check systems. Many doctors reorder tests or check the parameters with other calibrated devices when the values are not tallying with the clinical context.  

Unintended harm, both mental and physical, that can result from self-monitoring is not well studied. It is increasingly observed that these practices are leading to high levels of anxiety, occasionally depression, obsessive compulsive behaviors of repetitive and frequent monitoring, and self-medication leading to medication errors. There is also a potential risk of healthcare providers exploiting the vulnerability induced by this anxiety. All of the above have been amply evident during the ongoing Covid pandemic.  

Advances in digital and biomedical technologies, and disruptive changes in the way healthcare is being delivered are enabling people to access healthcare when and where they need it. Like every technology, these too have enormous potential for unintended harm. People should learn to use technology and not be subsumed by it. While there is no harm in self-monitoring as per the appropriate need, it should be ideally supervised by a qualified health professional. People should desist monitoring or getting tested more often than needed. They should not try to interpret the values themselves, unless they have full understanding of them. 

Basic understanding of commonly monitored parameters

Pulse rate 

Normal values for pulse rate range from 60 to 100. In athletes and people who regularly exercise, resting pulse rates can be lower than 60 and are perfectly normal. Variation in pulse rate over 24-hour period is perfectly normal and is physiological. Heart rates above 100 are normal during or immediately after physical exertion, any physical discomfort, mental stress, excitement, fever etc. Sometimes devices may wrongly display low heart rates due to extra beats that are not sensed. 

Blood pressure

BP should be recorded after resting for 10 to 15 minutes. Proper application of the cuff around the arm is important. Correctness of the size of the cuff in comparison to the arm size is also important. The devices should be calibrated periodically against the standard mercury manometer. Blood pressure is normally expressed as ‘systolic’ and ‘diastolic’ blood pressure. Normal values for systolic blood pressure are 100 to 140 mmHg and for diastolic blood pressure these are 60 to 90 mmHg. The term ‘low blood pressure’ is generally applied to systolic blood pressure of less than 90 mmHg. People need not be worried about low diastolic blood pressure, which is commonly seen in elderly people due to thickening of blood vessels with ageing. Just as heart rate, systolic blood pressure rises with physical exertion, mental stress, pain, excitement etc., and is physiological. Rechecking blood pressure after resting or relaxation or medication for pain and other discomforts will confirm that it has become normal. 

Oxygen saturation

This parameter is not measured routinely even during routine consultations. Normal values range from 95 to 100%. However, people (especially chronic smokers) who have chronic obstructive airway diseases or who have underlying sleep disorders (snoring with apneic spells and day-time sleepiness), will have saturations from 88 to 92% without any symptoms. People with dark skin tones have a higher skin pigmentation which can interfere with the readings by overestimating oxygen saturation and can thus cause people to miss low levels. 

Monitoring oxygen saturation is useful in people who have either acute and chronic lung or heart conditions. The values can guide in the decision for hospitalization, initiating oxygen therapy, and in starting certain medications. People infected with Covid-19 are asked to check oxygen saturation while resting and then after walking for 6 minutes. A fall of oxygen saturation levels by more than 3% or a drop in levels below 94% provides an early warning for hospitalization or arranging home oxygen if there is an acute bed shortage. 


A reliable weighing machine is an important self-monitoring tool. Obesity is a rapidly growing epidemic across the world. Childhood obesity is increasing alarmingly. Regular weight monitoring is useful in guiding lifestyles. It is preferable to measure one’s body weight after the morning bath before dressing. Body mass index (BMI) is used to define what is overweight and obese. It is calculated as weight in kgs/ height in meters squared. For example, a person weighing 70 kgs with a height of 170 cm will have a BMI of 24.22 (70/ 1.72). As per western definitions, a BMI of 25 or less is considered normal, 27 and above as over-weight and 30 and above as obese. For Asians, a BMI of 22 or less is considered normal and 27 and above is considered as obese. 

Weight monitoring is most useful in patients with heart failure. An increase of 2 kgs over a week is suggestive of worsening of heart failure with increased fluid retention. It will guide a patient in reducing his/ her salt and fluid intake and increasing their diuretic (drugs that remove salt and water through urine) medication.  

Blood sugar

Glucometers are one of the earliest self-monitoring tools. Blood sugar monitoring is most useful for people with poorly controlled diabetes, requiring multiple doses of Insulin. People whose diabetes is controlled with oral drugs may not need home monitoring of blood sugars. Glycosylated hemoglobin (HbA1C) is measured once in 3 months for those with A1C values above 7% and once in 6 months for those with A1C values below 7%. 

Glucometers using finger prick measure capillary blood sugar, while sugars measured in labs using blood sample measure venous plasma blood sugar. Plasma blood sugar is ~11% lower than capillary blood sugar. Glucometers, like many electronic devices, require periodic calibration with standard lab-based test. It is advised not to squeeze the finger for drawing blood through a finger prick. That might result in false lower values. 

Take home message

Home monitoring is convenient and highly useful for both selfcare and remote care. It has the equal potential to harm if not used judiciously. Basic understanding of normal range of values and their correct interpretation are essential for proper use. Home monitoring is more useful for remote care by a qualified health professional than selfcare. 

Dr Krishna Reddy Nallamalla
President, InOrder
Country Director, ACCESS Health International

Photo Credits: Market Research Biz