Blood pressure of 100 over 70 in women: when low is too low

A reading of 100 over 70 often causes concern, because it is so clearly below everything you usually read about. The reassuring answer first: low blood pressure without symptoms is not a medical finding.

That is the key difference from high blood pressure. High blood pressure causes harm even when you feel nothing – which is why fixed thresholds exist for it. Low blood pressure does not cause silent damage. It only becomes relevant when it causes symptoms.

What counts as low

As a rough guide, blood pressure below 100/60 mmHg in women and below 110/70 mmHg in men is considered low. At 100 over 70 you are therefore at the lower end of normal, not below it.

An important point for context: there is no separate threshold table for women. The classification of high blood pressure is the same for both sexes. What is true is that women before the menopause have slightly lower readings on average – a statistical difference, not a separate standard. The full classification is set out in Blood pressure chart: what your numbers mean.

When it is harmless

If you feel fit and well and do not get dizzy when standing up, 100 over 70 is simply your blood pressure. Low resting blood pressure is common in slim, young and athletic people and is statistically even associated with a lower cardiovascular risk.

In this case no treatment, no tablets and no special monitoring are needed.

When it should be checked

Things are different if symptoms occur:

• Dizziness or vision going dark when standing up
• Brief fainting – even if it was “just once"
• Persistent tiredness, difficulty concentrating, a drop in performance
• Cold hands and feet together with palpitations
• Nausea or shortness of breath on light exertion

Then the problem is not the reading itself, but the question of its cause. Possible causes include dehydration, anaemia, thyroid or adrenal disorders, side effects of medication or a problem with circulatory regulation when changing position.

Newly occurring low blood pressure deserves particular attention. Anyone who had 125 over 80 for years and is suddenly at 100 over 70 should have this checked by a doctor – a change is more meaningful than an absolute value.

The gap between the readings

100 minus 70 gives a pulse pressure of 30 mmHg. That is low, but not yet unusual. An average gap below roughly 25 to 30 mmHg can mean that little blood is pumped out with each heartbeat – if shortness of breath, dizziness or a drop in performance occur as well, this should be checked. More in Pulse pressure: what the gap between your blood pressure readings reveals.

The special case of pregnancy

Blood pressure often falls during pregnancy, especially in the second trimester – this is a normal adaptation. Dizziness and circulatory problems are common. Nevertheless, any noticeable change in blood pressure during pregnancy belongs under medical care, in either direction.

What helps in everyday life – if symptoms are present

These measures are generally recognised and do not replace investigating the cause:

• Get up slowly, especially in the morning – sit up first, stay seated briefly, then stand up.
• Drink enough. If you have to limit your fluid intake because of a heart or kidney condition, stick to that limit.
• Exercise – regular endurance activity stabilises circulatory regulation.
• Alternating hot and cold showers and compression stockings are often recommended.
• Several smaller meals instead of a few large ones, as blood pressure can drop further after eating.

On the subject of salt: people with low blood pressure are sometimes advised to eat more salt. This is not a general recommendation – discuss it with your doctor before changing anything.

Measuring correctly pays off here too

Low readings are also distorted by measurement errors. One week with two measurements each morning and evening, each with your pulse and a note on any symptoms – your doctor can do far more with that than with a single number. The sources of error are described in Measuring blood pressure correctly.

When you should seek medical advice

• If you faint or nearly faint
• If your blood pressure is newly low or has dropped significantly
• If you have persistent tiredness or a drop in performance with no explainable cause
• If you take blood pressure-lowering medication and your readings are low – the dose should be reviewed by a doctor, but not changed on your own

In case of loss of consciousness, chest pain or shortness of breath: call the emergency services on 112 immediately.